>>105770273 (OP)open source is the license. Even if the code is available like FUTO apps, Brave or leaked GTA source codes, it doesn't mean these proprietary software are open source. These all are closed source, proprietary software and you can't compile the binaries 1:1 and the end result will be different than the official binaries.
If you would use source code from proprietary software, you would be sued.