You're quite correct, the Open Core model (and, to some extent, the proprietary relicensing system as well) is made possible because of the way copyleft works.

You're quite correct, the Open Core model (and, to some extent, the proprietary relicensing system as well) is made possible because of the way copyleft works. I've previously written that <a href="http://www.ebb.org/bkuhn/blog/2009/10/16/open-core-shareware.html>GPL http://www.ebb.org/bkuhn/blog/2009/10/16/open-core-shareware... is only a tool, and the tool can be used for good things and bad things too</a>. I also agree that permissive licensing is <em>much better</em> than GPL+OpenCore.