Jeremy Tregunna wrote:
>
> Not necessarily, the license just must not explicitly forbid commercial
> sale to be GPL compatible.

>From Richard Stallman:

" The 'Ruby license' does not give permission to sell copies.
  So it is not a free software license.

  Only the fact that Ruby is also available under the GPL
  makes Ruby free software "

In order to be GPL compatible or to be free software (according to the
FSF, at least ), you must explicitly protect all of the essential
freedoms of free software.

For the specifics:
http://www.fsf.org/licensing/essays/free-sw.html


> Can't we all just get along?

Sorry... couldn't help being a bit facetious there.
But you're right, it was unnecessary.