FreeBSD: The Power to Serve
The GPL and BSD Licenses
•The GPL mandates that source code be disclosed
•The BSD License allows source code changes to be kept secret
•GPL is often categorised as "Copyleft", as distinct from "Copyright" •BSD License is "Copycentre".  We actively encourage third parties to use the source code. •Donating changes back is purely at the discretion of the party making the changes