As for -perl or -cpan suffixes, feel free to do so. Just don't expect me to do so. The added benefit is certainly not "Clear" to me.
The benefit is that "libnet" (a C++ project, maybe the original project) won't clash with "libnet-perl" (the CPAN module). Also, if you're searching for a CPAN module on github, it helps if you can apply simple logic to get to the name of the github project instead of trying three different possibilities.
My only thought is a question, why is a standard needed, and what is its benefit? And furthermore, who's going to control it if you were to start one?
I'm not proposing a compulsory standard (which would be impossible to control anyway), but a naming convention like on CPAN: Sure, a couple of extroverted personalities are squatting in the top level namespace (Mr Ingerson comes to mind), but the majority are good citizens who get along just fine.
One could argue that github should take control of this, but I'm afraid the genie is out of the bottle already.