GitHub represents open and democratic code. It symbolizes digital beauty distilled by the knowledge economy masses (its actually thanks to git and Linus, but nevermind that right now...)
Microsoft, on the other hand, is the king of uncool, buggy, god-forsaken software that never works like Winblows and Office. In fact, I contend that their dominance in the market has resulted in ~100 billion in lost productivity annually in the US alone, and is directly responsible for the rise of IT/Network admin as a real profession.
Bill Gates is a genius philanthropist who has dedicated the second half of his life to undo all the damage he did with Microsoft. Bill, you kicked ass and now you are forgiven.
So now they have hired a CEO that looks like a cross between Steve Jobs and a yogi master and eats nothing but quinoa all day, and followed that act with buying cool companies such as GH. Now you do the math...