Anyone can invite rms to speak, and given some minor conditions, he will come. He will come and talk because he believes that everyone deserves Free Software.
This is not monumental in any sort of "MS and the FSF coming closer together" sense.
It was very nice of Microsoft to invite him though, but not more impressive than, say, a University or hackfest.
Oh? Here [1] he wrote this:
> I am selective about the events I participate in. If you are inviting me to speak at a larger event, please inform me now of the overall nature of the event, so I can make an informed decision about whether to participate.
Mr Stallman was at Microsoft Research, btw. It is a specific department of Microsoft.
[1] https://groups.google.com/a/mysociety.org/forum/m/#!msg/myso...
It is more impressive than speaking at another venue because this just shows how open minded they’ve become now and I give them great credit for that if not anything else. Satya’s created such a seismic shift in mindset there in such a short time.