@mcc Did copyleft licenses ever meaningfully restrict the behavior of large corporations? Licenses are effectively a statement of intent with respect to future litigation, and if the copyright holder is not willing or able to actually *perform* that litigation, everyone gradually understands that this is a Mexican standoff where one side's guns aren't loaded.
@glyph Redhat establishing that its GPLed software is no longer available under the GPL seems to indicate the answer to your question is "no".