Khoi Vinh together with Allan Cole have released (a rather noisy) grid based WordPress theme called Basic Math.
They say it’s GPL, while the price tag reads: “Single-site License (Limited time only) $45″, which clearly violates one of the main freedoms protected by GPL — the freedom to run the program, for any purpose (freedom 0).
Update: Basic Math is now fully GPL.
Good catch! Has this term been removed? I can’t find it on the Basic Math site.
Another possible issue is the version of the GPL. If we accept the interpretation that all WP plugins and themes are derivative of WP, then I’m not sure the right licence is the GPLv3. WordPress is released under the GPLv2, and, as far as I know, there is no “or any later version” term anywhere in it. (This, of course, would apply to all themes and plugins, not just to Basic Math.)
demetris, thanks for the tip — they have indeed removed that requirement.
Regarding the version of GPL — you are right — WordPress is GPL 2 and so should be plugins and themes.