This is good not bad. Their improvements are available under MIT license. They would have been fully within their rights to not release and put in a proprietar

This is good not bad. Their improvements are available under MIT license. They would have been fully within their rights to not release and put in a proprietary product but did not do this. Instead everyone can benefit from their improvements. Author can steal whatever he wants for his upstream. (I can’t find any details of “Microsoft MIT” and the above is premised on it being functionally MIT.)