Jeff Atwood and Ben Collins-Sussman both believe that there are two distinct camps of software developers: The "20%", and the "80%".
The 20% folks are what many would call "alpha" programmers
The problem is that Sussman largely defines the 20% as actively participating in open source projects. In fact, it's so important, that he mentions it twice in his article.
I agree with most of his definition;
These folks were the first ones to install Linux at home in the 90's; the people who write lisp compilers and learn Haskell on weekends "just for fun"; they actively participate in open source projects; they're always aware of the latest, coolest new trends in programming and tools.
But I don't agree with the emphasis on open source. In case you're wondering, Sussman is one of the original architects of the Subversion source control system (which is open source).
I know many programmers who I would consider to be in the top 20% of the field. Most of them have made no contribution to open source at all. Why? There's not a hell of a lot of money to be made in Open Source.
I'd rather spend my spare time earning more money, than writing and releasing code that other people can profit off. Does this make me a worse programmer? I don't believe so. There are many programmers that are every bit as competent as the guy who wrote PHPNuke or SQL-Ledger. They just choose to make a living from it, instead of release it to the world for free.
There's many brilliant people who don't contribute to Open source. (Contrary to popular belief), many of the developers at Microsoft are bright as hell. Ditto Google. Is the source code for Google's search engine available?
Your merit as a software developer is not defined by your contribution to open source. It's defined by your passion.