I am developing an Android app and I need chess pieces images for my it. I am concerned about copyright issues as well. I can copy images from other chess apps on GitHub projects, but I am not sure if that is legal. Is there any free source to get images of chess pieces?
Check out the licenses of the piece sets that lichess uses: https://github.com/ornicar/lila/blob/master/COPYING.md#exceptions-free
Personally I am using the cburnett piece set for my project.