By pelegri on Apr 30, 2010
We introduced dual-licensing into GlassFish back in November 2006 but, somehow, people still get confused about how it works. It really is pretty simple (and not as complicated as quantum mechanics) but legal explanations by laymen always encounter IANAL...
... which I'll bypass through links and excerpts:
From Wikipedia, check out: Multi-Licensing, specially the "License Compatibility" paragraph. Do note that, in the case of GlassFish, we are talking about two OSI-approved licenses: CDDL and GPLv2 w/ ClassPath Exception.
Closer home, check out this excerpt from the Q&A on NetBeans 6.0:
Q: How can something be released under two licenses?
A: Dual-licensing is the practice of distributing identical software under two (or more) different sets of terms and conditions. When software is dual-licensed, recipients can choose which terms under which they want to obtain the software. The two usual motivations for dual-licensing are business models and licence compatibility. In the case of NetBeans, we're distributing the code under two licenses, CDDL and GPLv2 with Classpath Exception, for license compatibility. That will allow code from differently licensed free software projects to be combined with NetBeans, and will give our users the choice to pick a license that they feel more comfortable with...