uClibc is a fork of an old and obscure libc, which later incorporated some code from glibc and a few other libc implementations. They're all GPL'd so the mixing

uClibc is a fork of an old and obscure libc, which later incorporated some code from glibc and a few other libc implementations. They're all GPL'd so the mixing of code probably isn't carefully regulated, and figuring out what stuff is appropriate to submit upstream or what is even derived from a particular upstream source is probably not trivial.