== Open Core == 

 It seems this sort of legal arrangement (open source + copyright assignment with rights to use proprietary licenses) is called "open core", which might warrant another article.  Some links: 
 * http://blogs.computerworlduk.com/simon-says/2010/06/open-core-is-bad-for-you/index.htm 
 * http://ebb.org/bkuhn/blog/2010/10/17/shuttleworth-admits-it.html 
 * http://www.channelregister.co.uk/2010/07/20/why_nasa_is_dropping_eucalyptus_from_its_nebula_cloud/ 
 * http://www.ostatic.org/blog/open-core-or-open-snore 
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