Although Stallman argues otherwise, the nature of the GPL is really incompatible with how business is done in the real world.
Red Hat deals heavily in GPL'd code that it writes and maintains. It is a major contributor to many, many GPL'd open source projects. Even where it cannot get patches accepted upstream, they maintain many year, massive patch sets to satisfy needs of corporate clients. How do you explain their success? The same is true, to a lesser extent, for SuSE, which has a major economic footprint in corporate Germany (and Austria and Switzerland).
And how about The Qt Company or MySQL / MariaDB?