My comment was not about giving credit. The point is that if you know that the system is GNU, you know what software it is supposed to run, and that does not mean that it can not be compatible if it is not GNU. We can probably also use POSIX (btw, the name for the standard was suggested by RMS [1]) as the lowest common denominator, but would that also include Android?

[1] https://stallman.org/articles/posix.html