Microsoft's recent partnership with Novell only underscored concerns about Mono -- particularly given that Novell is the primary sponsor of the project. Foremost among these has always been the issue of intellectual property. Critics warned that, despite de Icaza's and Microsoft's protestations to the contrary, Mono exists solely at the whim of Microsoft. Anytime Redmond felt like pulling the rug out from beneath them, Mono developers could find themselves subject to patent-infringement lawsuits.
As part of its agreement with Novell, Microsoft has now enumerated a short list of those categories of developers that it promises not to sue. The implicit message is that everyone else should watch out -- and watch out they shall. The availability of Java under the GPL now gives those developers who want modern language features an alternative to Mono, and they need never look back.
If they didn't, though, it would be a shame. Java is a welcome addition to the oeuvre of the open source community, but it takes away nothing of the technical merit of Mono. With both platforms available under open source licenses, a commingling of their technologies could lead to a new, open system that's an evolutionary step ahead of either of today's offerings. Sun, which has some experience navigating patent issues, could assist in guiding this effort.
Unfortunately, I suspect that the fallout of the Microsoft/Novell deal will succeed only in balkanizing the open source community, such that projects like Mono will fall by the wayside over ideological differences. If that happens, I fear Microsoft will have won yet another victory.