I believe that Microsoft, under Satya Nadella, understand the difference between short-term and long-term gains. Acquiring GitHub and leaving it the way it is, or advancing it, is a long-term gain; I have literally switched a project from another language to .NET Core due to their open-source 2.1 release. Trying to "monetize" it would be a short-term gain, but a long-term loss.
I get that MS positioned itself as the enemy of open source software many, many years ago. I also understand, as a dev who's been around their technology since 2001 tangentially, and 2004 in earnest, there has been a shift in their thinking. Nearly all of the .NET Framework is now open source, and the entirety of .NET Core is open. Visual Studio Code, a lean-and-mean editor that, IMO, is "VS without the ceremony", is a phenomenal product, and built on GitHub-developed technology to boot.
MS has been doing their dead-level best to earn their open source chops for several years. When Rackspace acquired SliceHost, I was nervous; when they announced their plan for minimum-$50 bills for every client, I moved to Azure. While I currently find more value with Digital Ocean, even then, I could create an Ubuntu VM in Microsoft's cloud. The way my desktop is set up, I can click an icon and launch an Ubuntu instance on my computer that plays nicely with Windows (and my local filesystem). I still use Azure for files; I've got a combined 9-year archive of podcasts hosted there, plus nightly backups, and my bill is less than a dollar a month.
This news makes me happy; it tells me that GitHub is going to be here for many years to come. The old MS would have tried to convert us to TFS or Visual SourceSafe in 2 years; this MS actually shut down its own hosted solution, CodePlex, in favor of GitHub. The naysayers / doomsday-soothsayers haven't been paying attention.
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