Harmony’s curiously flat tune

“Although the concept of copyright is anathema to many free
software advocates, it can be considered the fundamental force of
both copyleft and open source software. Copyleft licences like the
GPL subvert copyright to ensure source code is always made
available, while permissive licences retain credit, at least in the
source code, for the original authors. As a fundamental force, if
you can gain control of copyright, you gain a lot more power.

“This is, for example, how a company that has a GPL-licensed
community edition of its software can also sell a
proprietarily-licensed enterprise edition; it has ownership of all
the rights, either because it wrote all of the code or because
anyone who has contributed code to it has signed over their
copyright.”

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