[drupal-devel] Licence issues using GPL'ed SquirrelMail code in mailhandler.module?

Hello all , I'm making improvements to the mailhandler (and fixing the drupal_special_chars problem by replacing with check_plain). SquirrelMail already implements a very thorough URL parser, attachment handler, and mail re-wrapper. SquirrelMail is GNU GPL, so I'm wondering if I can re-use that code rather than reinvent. What are the licence implications? Do we simply need to credit the SquirrelMail project and redistribute the licence intact? Regards, Mark