There are a lot of open source games, such as Flare (Diablo clone).
Is it OK to re-use the art they put in their open source game and make a profit?
I'm the Flare creator (main developer and main artist). Drop me a message if you have specific questions.
All of Flare's art can be reused commercially. Some assets are CC0, some are CC-BY, some are CC-BY-SA. It's important to know the requirements of each asset you use and that you credit each artist.
Share-Alike assets can only be remixed with other Share-Alike (or compatible) assets. Because of this many commercial games choose to not include CC-BY-SA art.
This will depend entirely on the license applied to the art assets. The number of open source licenses is always growing, so attempting to provide a list here would be pointless.
You will need to research the specific license that's applied to the art. Some of these licenses will allow you to reuse the art. For example, in the link you provide, a majority of the art is licensed under CC BY 3.0 which states you're free to make commercial use of the work (as long as you attribute the author).
If you're unsure what your rights are, you might try contacting the owner of the rights to the art and ask about your intended use. You may also ask for permission to use the art beyond what the original license states or work out a deal for such permission.
Publication of copyrighted works of art requires the author's consent with due exceptions and limitations that normally apply. Whether the game the art is used in is open-source, is irrelevant. However, in the spirit of this openness, it is not uncommon (but also not necessary) for the author of the game to automatically grant a liberal license to his work. The author's permission is still required, but implied, often conditionally.
If such a license is not provided or you do not wish to adhere to its conditions, and the art you wish to copy is protected by copyright, legally, you can either:
You are free:
- to Share — to copy, distribute and transmit the work
- to Remix — to adapt the work
- to make commercial use of the work
So yes, you can re-use and make a profit from some open source game art, as long as you attribute the author of the art.
Attribution — You must attribute the work in the manner specified by the author or licensor (but not in any way that suggests that they endorse you or your use of the work).