[belorn]

Companies that avoid GPL also avoid licenses that forbids DRM and guaranties access to source code.

But to reiterate the four freedoms:

Freedom 0: The freedom to run the program for any purpose. With DRM this is impossible. The DRM business model to prevent generic parts rely on users not having freedom 0.

Freedom 1: The freedom to study how the program works. Without this researchers can't do inspection of medical software or voting machines.

Freedom 3: The freedom to improve the program. Without this a person can't improve their tractor that they bought, even if they are by law the private property owner of the device.

That leaves:

Freedom 2: The freedom to redistribute and make copies so you can help your neighbor.

So for the cases above, three out of four software freedoms is required.