Even though Red Hat has outright rejected entering into any patent agreement deals with Microsoft claiming that “open source and the innovation it represents should not be subject to an unsubstantiated tax that lacks transparency”, Red Hat's executive VP of engineering Paul Cormier recently said that they are willing to work with Microsoft on the interoperability front.

"I want to talk to the folks at Microsoft about our two operating systems and how we can work together to solve real customer problems without attaching any unrelated strings, such as intellectual property," Paul Cormier, Red Hat's executive vice president of engineering said.
Microsoft's senior vice president for server and tools Bob Muglia said the company would be happy to work with Red Hat and others on interoperability, nevertheless, he noted that the issues of interoperability and intellectual property are not completely separate, and have to be considered together.

While the two sides are still disagreeing about this fundamental issue, they also seem fairly interested in working out some kind of deal. Could Red Hat be next in a patent agreement with Microsoft? An article over at DesktopLinux.com makes some interesting arguments and speculates they definitely will, and if so, the remaining major Linux distributors could have a hard time holding out.