They need developer mindshare and they lost a lot of developers in the 2000s. Buying GitHub (and being involved in 100s of projects) brings this mindset of Microsoft as a developer company back to developers. Like as an advertisement platform/branding for some novel technology like this CoPilot.
Does anyone have the numbers before they bought github, I saw them once, don't remember the values, just remember being shocked at what percentage of the total github code base was Microsoft. I had no idea they were using it at all.
More explicitly, how would a license that gives everyone the right to copy, modify and redistribute source code for any purpose without compensation or attribution have prevented Github from building a tool that copies, modifies and redistributes source code without compensation or attribution?