It's okay: this is also an opportunity to show that they can play well with others. Done correctly they can build trust within a community that has traditionally disliked them.
Yeahhhh, because developers like you and me are assigned the IP... Nope. We take a home paycheck but relinquish the IP to MS. What you're suggesting is tantamount to Walmart employees taking offense to Kmart for copying "everyday low prices". Sure, a real live human being came up with that tagline, but do you think Kmart or Walmart send them checks every month for the benefit derived for the now famous line? The open source world is different. In many cases individuals do maintain ownership of their IP. And when they don't, often it is held by a trustee for the benefit of the community.