If that increased the "surface area for copyright/patent infringements" were so great, or were such a dramatic burden, then the above would not be true. But it is true.

Let's look at Cassandra as an absolute prime example of what I'm talking about. The original version of Cassandra was a code drop by Facebook. It made some news in tech blogs, and then mostly everyone forgot about it. A few months later, another version was dropped, but this time nobody really noticed.

Then Jonathan Ellis found the codebase, imported it into GitHub, and started doing development on it in the open, and accepting patches. Sure enough, more people started to take notice and watch as development happened, and started to contribute back. A community started forming. Facebook then donated the project to the Apache Software Foundation, where it's continued to be developed in the open and thrive. Now it's supported by many companies; in fact new companies have sprung up specifically on the premise of providing support for it.

Empirically speaking, the software has had much more development since it switched to being developed in the open. Subjectively speaking, it's simply a vastly improved piece of software from when it was handled as a "code drop", it's boosted Facebook's credibility in the eyes of developers for having started the project, and it's gained much more popularity.

So, going back to F#, what are the goals that Microsoft is trying to further with its platform? I'll posit three (of which there are certainly more): to increase the reach of the .NET platform, to boost Microsoft mindshare, and to increase developer productivity.

Each one of those goals are served better by moving to an open development model, for fairly obvious reasons.

I didn't mean for this response to become so long, but it just seems to me that this is such an obvious and unfortunate blunder that it renders the whole open sourcing of the language nearly worthless.