Perl is available under a choice of the GPL or the Artistic License. I have it on good authority that the Artistic License was designed to be easy to drive a truck through.

Apparently there is a desire to tighten up Perl 6's licensing somewhat. But not too much - after all a number of key Perl people are big BSD fans who detest the GPL. Larry Wall doesn't want to drive them away.

Cheers,
Ben