En:Does the GPL require me to publish the source code of modified versions?

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Question: Does the GPL require me to publish the source code of modified versions?

Answer:

The GLP does not require you to make your modifications available to the public. You're free to modify the source without ever publishing it. This applies to organizations and companies as well - everybody is allowed to modify a GPL'd program and use it internally without ever publishing it.

However, if you plan to publish the modified version in any way, the GPL requires you to make the modified source code available to the users of that modified program.

This means that the GPL allows you to publish modified versions of a program only in a specified manner, the decision about whether you want to publish the modifications at all is up to you.