But they did and are doing the very wrong thing - they lied and mislead everyone. Pretended they are doing "research" and claiming its all for "science", getting all of that data for free, ignoring the licensing with no one opposing and then all of a sudden selling themselves to Microsoft. If Microsoft went out and said that they are going to collect all open source code available publicly to create a commercial product for generating the code - there would be massive protests I can tell you that. They would want to prevent MS from doing that and maybe even force it to release software as Open Source. Sneaky cheeky way this got monetized is something that really annoys me.
Also all I heard they took all code available in github - I didn't hear anything about MIT license only. They probably just took everything. And even MIT and any other license - Never Allow To Take Out the Author. You need to attribute the author! And GPT is not doing that. To me this is breaking the license law and the using the code from GPT in your own - you might end up in legal issues.