And what would be the benefit if Microsoft gave you credit for it? Most likely their lawyers would reject it since you may then be able to sue them for...I don't know what, but money in any case.
It's a very Microsoft-thing to do to copy someone else's idea and improve on it (C#, RDP, Excel). If you release something as open-source you have to ask yourself if your doing it out of altruism or for money? In case of the latter you have to plan accordingly, by patenting or with restrictive licensing.
Regardless of the legal case, the idea that concerns of reputation or credit are irrelevant to open source work is a crock. People may be working on open source because they genuinely want to help others, but if you deny them credit for the work they did then you can very well expect the well of open source innovation to dry up pretty quickly. And for a company like Microsoft, reputation is exactly why they are contributing to open source in the first place.
I'm not even sure if the author's idea was original anyway. It looked more a CLI program to download and run installers.