Are you aware how github works, or open source development in general ?

Some users are developers, too.

Some people write code, others may try it out, and a few of the latter might help with developing it. And some of these efforts become popular.

That's how we have Linux or KDE.

That's why Sourceforge was such a big win, why Ubuntu has launchpad and ppas, and why Arch has AUR.

It is all based on open sharing.

And of course you can opt to not run code that you don't know, or don't understand , or don't trust.