There are a number of licenses that are compatible with GPLv2. The Free Software Foundation's take on which are and which are not (and why) is here. <http://www.gnu.org/licenses/license-list.html>. They also have a couple of relevant FAQ answers here. <http://www.gnu.org/licenses/old-licenses/gpl-2.0-faq.html#WhatIsCompatible>. Best regards, Paul