I am bit more cynical about this. Google and others have simply shown Microsoft how to make loads of money by opensourcing the project, while still keeping the upper hand on it. How to "opensource-but-not-quite-opensource" (Chrome/Chromium, Android/AOSP,...) the projects. Even Amazon didn't succeed in prying away Android from Google (Fire). So in my mind it's actually surprising that it took them so long to join the party. After all, what do they care if Linux is running as part of Windows, as long as they can sell the Windows licenses? It's not like "the year of Linux desktop" is coming anytime soon... :)

I think the real danger to these companies are less-than-free licenses (think Commons Clause) which give most of the freedoms to the user, but still allow the original creators to retain some of the rights, making it possible for them to have a business model behind it (such business model that AWS^Wbigtech can't take away so easily). And in this case RMS is doing more harm than good by preaching about "pure freedom". Of course Microsoft is on the same side as he is. "Write the code, but give it away". What's not to like?