Private people would keep their code locally and share the snapshot of the code using any file sharing or hosting option available.

Companies had been hosting their own CVS or later svn servers.

> How did people do it before github? Did everyone write everything with peek and poke?

I've been sharing GPL projects since 1999. We didn't need peek and poke (Both of which I have also used further in history...), but we managed nevertheless.

Prior to github I shared software on sourceforge (and others). Prior to that I published stuff on Freshmeat.

Prior to that I downloaded games others shared (not open source) on Happy Puppy.

Prior to that I used usenet to find and download games, shareware, etc.

Prior to that I used ftp to (IIRC) ftp.sunsite.edu, ftp.nic.fi, and others.

Prior to that I got news of new releases using Gopher.

Finally, prior to that, I actuallyy did use peek and poke to write software :-/

If github went away, and centralised repos went away, we'd still have something...

Sourceforge