Well first let me tell you the events that lead me to this conclusion. My initial idea was to create an open source 3D shooter, because there was no actively developed 3D shooter for years now, so I thought I just make one on my own. I thought it cannot be that hard, since open source gives you so much benefits, like using other people's work and combining it to something new, so you end up with much less work. There were certain things on my checklist of what I need like:
1. Open Source game engine
2. Open source game code
3. Open source game art
The open source game engine I had already found. Open source game code that was universally usuable was basically nonexistent, since it was mostly engine or game specific, so I already accepted for me that I probably have to do the game mechanics programming from scratch. Open source game art was the point I had the most expectations from, I thought I can build a full game out of open source game art that was made by others and already ready to use. I did some investigations before, if open source game art is available in large quantities and it was, so I did not enter this project without investigating first. Thinking it can save me lots of work I searched basically the whole internet for open source game art and downloaded everything that seemed to fit, this of course took some time. Then I made a big archive with all the content I got and sorted it all so I can better access it later when I need it. While doing this I already encountered the first problems:
1. Not enough content of a certain kind or style was available
2. Too low quality content to be usable
3. Unfinished content that would require significant work to finish
4. Inconsistent art style, since every artist has his own style
5. Restrictive licenses especially GPL (who the hell applies GPL to art and how is that even supposed to work?)
6. Incompatible art created for another purpose
7. Total incompetence of the creator, resulting in a major mistakes that make the art asset useless, even if it looked good
8. Illegal content, many release content as open source that is incompatible with open source or downright stolen
9. You could do it better yourself, which removes the necessity to use open source entirely
So let us break down each problem, what other problems it leads to and how it has to be solved.
1: For the problem of not enough content available the solution is obvious, create it your own from scratch or pay someone else to do it, but paying someone else is too expensive so we are left with do it yourself. To be able to do it yourself you need to aquire a range of software or even hardware and to learn the skills yourself, which in the worst case can take you years to learn and thousands of dollars in cost for hardware etc. Yes theoretically the great open source community will help you creating exactly what you need totally for free if you just ask them, in reality this almost never happened, you only get ignored, if you find any open source artist at all. So due to its high unlikeliness that someone else will magically solve your needs, we can dismiss this idea. Only option we now have, if we do not want to do everything our own is to reduce the scale of the project and use only what we got, but the bigger the project is you want to build, the more unlikely it is you can get away with this. For example to build a 3D shooter with halfway decent quality, the minimum requirements are very high already and it is almost impossible to cover this with free open source stuff you find on the internet. So the verdict is if you face this problem, start to learn to do everything on your own or your project is dead.
2: Low quality content is always a problem, since open source game art gets created over a long period of time, the quality is often low. The biggest contributions to open source game art are things that someone else throws away because it is too low quality for the regular market. So you end up having to use other people's trash all the time, which may be fine for smaller projects with "intentional" low quality, but for serious game projects this is not an option. If your project grows and you eventually become better in your skill, you will likely find yourself wanting to replace or improve them anyway, which may result in even more work than not having used them to begin with, since you have to try to fix low quality material or replace it, doing all the work twice. Some might argue "Oh but this is good for placeholder art", but using placeholder art is not that practical, if you don't have a big team with a big budget. You can only use placeholder art if you want to do the programming first, but not release that placeholder art. Verdict if you face this problem, well "only" lower quality and eventually extra work, if you plan to improve later.
3: Unfinished content is very similar to the first problem, since having unfinished content is basically almost not having it at all. It is like having a car with 3 or 2 or no wheels at all, yes it may look nice, but you cannot drive it. Solution to this would be again to learn how to make art yourself and finish it, but if you can do it yourself, why bother fixing someone elses content and even having to credit them for it, because they chose a stupid license. Statistically the most common unfinished art asset is an untextured model, but from my experience the raw modeling is often not even half the work, more like 25% the work, 50% is texturing and maybe 25% implementation and this does not calculate in testing and optimization, since if you do testing and optimization you might find out, that the mesh architecture was badly made to begin with, so that it would have been less work to rebuild it your own from scratch. So if you face this problem, it is the same as the first problem, if you don't have the skills and potentially minimal time savings, if you have the skills. Sometimes it requires even more work to use someone elses unfinished art as a base, plus having to attribute someone else even though you did all the work.
4: Inconsistent art style is not that big of a problem compared to the other problems, since even though your game will look ugly, it will at least work and have all the needed pieces. So the verdict for this problem is, it is "only" ugly. It may even work for small game projects, but the larger and more serious it gets, inconsistent art style can be tolerated less and less.
5: Restrictive licenses can be a big problem. The irony here is, that open source licenses are supposed to be less restrictive, but some end up being even more restrictive. The worst people are those who apply GPL to art assets, how is that supposed to work? Does it mean you have to open source the whole game code plus assets under GPL as well, if you just use one small GPL image? Or do you have to GPL only the art? (Even though GPL is not supposed to be used on art) Or very liberally you have to open source only the GPL image again under GPL?! Nobody can really tell you, some even argue that art or data is magically not part of the program and therefore does not have to abide by the GPL license. Same problem goes for a lot of other licenses such as creative commons, since they are all slighly different and even there nobody really knows what the licenses mean exactly. Overall the more different licensed content you use the more trouble you have, since you cannot just simply release your game under one license, but have to provide a long list with attributions and license terms in the correct way every time. Verdict: Having different or restrictive open source licenses reduces the art assets you can use safely greatly, which is a big problem since when using open source art assets the choice is not that big to begin with.
6: Incompatible art is encountered a lot, since many open source digital art creators do not create it for games, but for render scenes or for movies, so if you encounter those, you may be able to fix it, but mostly you end up with totally unusable art assets. The worst part of this is that art like that often looks very good, since hey that is what it was made for, to look good, at the cost of having millions of polygons and hours of render time, good luck using that in a game. Verdict: Painful and frustrating, since you often have to throw away good looking art.
7: Incompetence is always a big problem, how often have I opened a .blend file totally not knowing what to do and the settings were so messed up I could not repair it. The art asset may be usable in some way, but since the author did not provide instructions, it is basically useless. It is like gambling, are you trying to figure out how to use it and / or how to repair it if necessary, or just make it on your own from scratch? This is similar to the third problem, you may end up having to spend more work into it, fixing someones broken stuff and even having to credit them for it, even though you did most or even all of the work. Some people will probably say, you can import the mesh into a fresh blend file, yes but you have to find first what to import and how. Even if you manage that, the asset will probably not work, since hey you threw away all the setup. Another problem are formats you have no idea how to use and how to import, or textures you have no idea how to apply. The other big problem is, that it requires a certain skill level to make usable game art, if major mistakes are made it can render the whole art asset useless. So if you are an artist releasing stuff as open source, please think about that someone else must be able to use it and cannot magically figure out how you intented it to be used. Verdict: Also painful and frustrating, since you are so close, but it still turns out to be useless.
8: Illegal content is probably the main reason I use less and less open source art. Potential illegal content can render a whole source like a website useless, since everyone can upload there, so you find lots of illegal content there as well. So you end up having to limit your sources greatly due to this problem and can only resort to sources that are credible and know what open source means. Opengameart is the only website that cares and is very safe, but I also found illegal content there after it being there for a long time. On blendswap I already found 3D models with textures with branding in it, since many people think all images from google are fine to use. Even on open source art websites you find a lot of people still using cgtextures even though they explicitely do not allow the use in open source at all, there is no debate on that, it is forbitten, but people refuse to learn. Verdict: Potentially very dangerous and can cause you a lot of trouble and shame.
9: If you can do it yourself, why bother with open source art? Yes, theoretically you safe work, but practically you also have to deal with all the issues I listed before, which may end up taking you much more work and trouble. My conclusion from this experience is, that most open source art is useless. For a video game, you need a large pallette of art with consistent quality, style and functionality, which is almost impossible to be fulfilled by open sourced art others released already. Yes there is a big exception here and that is raw materials, like texture photos, which I also offer here a lot, since having a large library of safe and ready to use raw materials can help you a lot, but the more specific the art assets get, the more you run into problems. To those people that might argue, that since I admit raw materials for asset creation open source art are not useless, the contept of offering open source game art in general is not useless, I say: If you have the skills to create the art on your own, why bother with ready-made open source art? Yes theoretically you safe work, but that is only if the creator is very skilled and did everything right and also meets the style you need, which practically is almost never the case. Raw materials are not art already, art requires that you do something unique with the materials first, a pile of mud is not equal to a sculpture.
Well that was quite a long article, but nothing compared to the time I wasted in my delusion thinking the concept of open sourcing game art works out as it currently is. I can imagine it could work out, but only if skilled artists take part in it, agree to producing content meeting certain quality and functionality standards. The anarchy idea to let everyone do as he wants, if qualified or not, does not work out, it needs a clear guidance, someone who controls the quality and especially the legality. For example browsing probably thousands of free 3D models I cannot remember finding even one that had LOD levels or collision meshes, which are pretty much standard in the gaming industry for over a decade now, or only one or two character models that were rigged and animated so that they could work in a game. So out of ALL the as open source freely available art assets, the number you can use out of the box in a game is basically very close to zero.
It is a problem of service, commercial asset stores give you exactly that, you pay, get the item and it works out of the box almost all the time. What the open source community has, you don't pay (which is nice), but what you get almost never works out of the box. If the open source community could progress to having a product that is at least somewhat useful, they could score with the free aspect, but a product that cannot be used is like a product that does not exist, it being free does not help much.
Yes, the open source idea COULD work out, but the way it is now, is just a pile of garbage.
PS: For those people who like to attack me with arguments like "Oh you are part of the community etc" - No, I'm not, they pretty much threw me out after not agreeing to their garbage production policies. I also think I fixed most of the issues (which nobody ever seem to have addressed before) listed here for me and as a result I'm offering asset store quality game art assets under the most liberal license available here on this website.