To find free Android game source code (not from APK files), you can explore several resources:

GitHub: Many developers share their projects on GitHub. You can search for Android game repositories using keywords like "Android game source code" or "free Android games." Look for repositories with permissive licenses (like MIT or Apache) to ensure you can use the code.
Open Source Game Engines: Platforms like LibGDX and Unity (though Unity is not entirely open-source, it has many free assets and tutorials) often have sample projects and community contributions. Check their official sites for example projects.
Game Development Forums: Websites like GameDev.net, IndieDB, and DevForum often have sections where developers share their source code. Look for threads or posts that offer free resources.
Educational Platforms: Sites like Codecademy, Coursera, or Udemy may offer free courses that include source code for projects. Even if the course isn’t free, the code might be accessible without enrolling.
Asset Stores: Websites like itch.io or OpenGameArt.org provide free game assets and sometimes complete game projects. Check their game development sections for source code.
YouTube Tutorials: Many developers share complete projects in their tutorial videos. You can often find links to the source code in the video description.
Reddit: Subreddits like r/gamedev or r/AndroidDev may have users sharing their projects or resources. You can ask the community for recommendations.
When using any source code, be sure to check the licensing terms to ensure you comply with any usage restrictions.