I say, if it's on cpan it's fair game no matter how you cut it. After all, for software to be useful it most typically needs to be distributable. I'm just saying there is a significant implied license (although I know that lawyers don't like that).

From cpan contributors part of the faq:

http://www.cpan.org/misc/cpan-faq.html#How_contribute_modules

However, I was surprised not to be able to find a place where you must agree to a license to upload.