Definition of "closed-source" [closed-source]

• Whose constituent makeup, or source code, is not made publicly available. (adjective)

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• "‘Open-source’ textbooks would be just as able to synthesize and publish that knowledge as ‘closed-source’ ones."
• "The protocols on all of these systems are closed-source the last I remember (2000 was the last time I touched a PLC)."
• "I believe VMWare, qemu and the closed-source version of virtualbox all provide USB support."