I think this may be what we're thinking of Luke:

While our directory is full of fantastic themes, sometimes people want to use something that they know has support behind it, and don't mind paying for that. Contrary to popular belief, GPL doesn't say that everything must be zero-cost, just that when you receive the software or theme that it not restrict your freedoms in how you use it.
from the Wordpress Free Themes Directory where they talk about commercially available themes.