What constitues a user is not unclear. A user is both someone who uses the compiled software (pushes the button in your example) or a developer capable of modi

What constitues a user is not unclear. A user is both someone who uses the compiled software (pushes the button in your example) or a developer capable of modifying the software. A developer doesn't need the freedom to redistribute the software to other users without also respecting their freedoms. Dual licensing does nothing to hurt freedom, as a user of the GPL licensed software your freedom is protect, both to use the software, and to modify it for your usage. Needing to assign copyright to make upstream contributions may hurt the rate at which the upstream project develops, but in no way hurts your freedom.