I've come across many programmers that can code well, but had horrible communications skills. It's always difficult to interact with these programmers. I spend more time extracting the meaning of what they're saying rather than getting work done.
... on StackOverflow.
Meanwhile, the great bulk of programmer communication is happening on blogs, mailing lists, and IRC.
You're very right that written and verbal communication is important, but you have to look in the right places for it.
[1] - http://github.com/defnull/bottle/ [2] - http://github.com/kangax
This happened to John Carmack, Jamie Zawinski. They are probably too busy in making stuffs work then writing answers on Stack Overflow or committing code to GitHub.
Also a lot of companies don't want their employees to write code for anyone else and will actually see open source contributions as a major red flag.
FUD. I work for a very large corporation, and open source was definitely not a negative when hiring me. Many very important parts of our business are based on open-source technologies. (And many aren't, FWIW.)
But if the code has copyrighted issues, then how can I show publicly? I usually have a copy of repository for my past projects and I don't mind to show it to people who interview me.
Also I think if I need to put code on GitHub, it has to be some software for more generic tasks.