From my view, Microsoft bought GitHub for 2 major reasons – access and information. Access is the first reason and it enables an extension of their own tools and cloud. My assumption is GitHub will soon find the first option for tools and for cloud to be Microsoft’s unique line up. Why would a developer publish to AWS, Oracle, Google, or IBM if a single button press got you the latest features and tightest integration by going to Azure. They won’t eliminate or block the others, they’ll just make Microsoft the default.
I don’t think Microsoft is buying GitHub to bury it or ruin it. Microsoft is not exactly the biggest promotor of open source, but they are an active player. This is not like Gillette buying the stainless steel razor blade patent so they could drag their feet on producing one and get more money out of their existing products. If Microsoft blocked GitHub, I think the world would just develop an alt-GitHub or shift to competitor.
The second is probably the more important: information. GitHub is where developers, programmers, and coders dream. They put snippets of code which are glimmers of the future. Simply understanding what libraries, language, databases, tools, and clouds are being used, frequency, and in what combinations will yield bright headlights into the near future. If you release a new library, you can now easily see its uptake in the community. Put more money into it if it’s yours, alter yours to look more like the winner, partner where you can’t win, or buy it up if it’s a good investment.
As long as Microsoft uses a respectful hand and doesn’t become the evil overlord, I think the purchase of GitHub will yield a bounty of information by which they can steer their own development of tools and products. For a company that has jumped in late on the Internet, Open Software, and Cloud, they sure do an impressive about faces.