OpenGameArt.org

Yes, you can use any of the art submitted to this site, even in commercial projects. Just be sure to adhere to the license terms. Artists often indicate how they would like to be credited in the 'Copyright/Attribution Notice' section of the submission.

If no specific instructions are given, a good way to credit an author is to include the following text in your game's credits file and on your game's credits screen: '[asset name]' by [author name] licensed [license(s)]: [asset url].

Yes, but only under specific circumstances. You must first make absolutely certain that the content has been released under one of the allowed licenses and attribute their work to them in the Author field. Failing to do so is plagiarism and will result in the work being removed.

You can request a takedown using the Removal Request form. Be sure to include the links to any art in question. Note that if your art is derived from a work that was a paid commission by OpenGameArt.org, the takedown request may not be honored.

The site supports licenses such as Creative Commons 0 (CC0), Creative Commons Attribution (CC-BY 3.0 and 4.0), Creative Commons Attribution-Share Alike (CC-BY-SA 3.0 and 4.0), and OpenGameArt.org Attribution (OGA-BY 3.0 and 4.0). Each license has specific terms regarding use and attribution.

The use of art in platforms like the Apple App Store depends on the specific license. Some licenses, such as CC-BY and CC-BY-SA, restrict the use of the work on platforms that include Digital Rights Management (DRM). Always check the license terms before using the art.

If you're the author of the work and you want to remain anonymous, just mention that in the description of your submission. This way, others will know not to attribute the work to a specific author.