According to the Wikipedia page on DotGNU [ http://en.wikipedia.org/wiki/DotGNU ], Mono doesn't just aim to by compliant with the Common Language Specification, but to maintain compatibility with .NET releases as they come out. DotGNU, on the other hand, is only concerned with implementing the standard. So, at least in theory, Mono could get into trouble where DotGNU wouldn't.

Still, this isn't making a lot of sense. My understanding is that Microsoft has been very helpful to the Mono project. But what really gets me is "it's a really good thing to have free implementations of C# but a really bad thing to use them..."

I would guess what he means is "It's good to be able to use the existing open source C# software, but please don't write any more of it"

> I don't get it. Why is the GNU Project developing their own C# implementation but is seemingly anti-Mono?

Did you read the article? Having a free C# implementation is important because it allows people to run their C# program on free platforms according to the FSF. However, writing and distributing apps in C# is not encouraged as people might get sued. RMS points that he has nothing against mono or any other free C# implementations (proof is that GNU has its own Portable.NET) as it allow people to move to a free platform.

That was my reaction. I would think that by publishing the ECMA standard (and there have even been revisions to the original standard), they have pretty much given up any patents on C#/.NET. Besides, if Microsoft was going to use their patents against open source projects, what would stop them from going after closed-source software as well?

Also, is there anything stopping anyone from writing an open source JIT that compiles C#/VB.NET/F# to Java bytecode? Or, converting .NET bytecode to/from Java bytecode? Then, you wouldn't be locked into a single system.

I'm actually working on a new open source project right now that is written in C# and is going to be released under either the BSD or MIT license (I haven't decided yet). So I probably couldn't disagree more with this article. I think that if more open source were written in C# or Java, it would be much easier to port Linux (BSD, etc.) to other platforms, since most/all of the software that people will want to use doesn't even need to be rewritten for that platform.

Publication does not affect your rights under patent law. In fact the patent itself is formally considered as publication (though in comparision to most RFCs, I find the writing style nearly incomprehensible).

"Publication does not affect your rights under patent law."

True, but letting Mono flourish for as long as it has without taking legal action against it opens up a can of worms that can screw with future action against it. Patent law recognizes the idea that implicitly letting someone infringe and not doing anything about it until it's most profitable for you/most damaging to them isn't the way the game's supposed to be played.

Add to that the fact that patent suits are the global thermonuclear war of the technology industry (the only way to win is not to play), and I'll be surprised if anything serious ever happens.

That's right, the longer they know Mono exists and let it slide, the more they risk losing an infringement suit over laches. But I don't think the existence of the ECMA standard matters.