RMS has just published a position paper against Mono. FTA:
Debian’s decision to include Mono in the default installation, for the sake of Tomboy which is an application written in C#, leads the community in a risky direction. It is dangerous to depend on C#, so we need to discourage its use.
The problem is not unique to Mono; any free implementation of C# would raise the same issue. The danger is that Microsoft is probably planning to force all free C# implementations underground some day using software patents.
This is the worst sort of fear-mongering. First of all, in addition to the better-known Mono project, the FSF has their own free C# implementation. The reason you haven’t heard of it is because it’s unable to compete on merit with Mono; its only (purported) advantage is its GPL licensing (Mono’s licensing is more piecemeal: GPL, LGPL, MIT, depending on the component).
Note that RMS is merely poisoning the well here; Microsoft is “probably planning” this or that, but there’s no halloween document; there’s no evidence of Microsoft every suing anybody over .NET; in fact the only public interaction Mono and Microsoft has had is to announce the (Mono) Moonlight project as the official Linux implementation of Silverlight. This means that a key part of Mono is the official, Microsoft-supported way to use C# code on Linux.
Oddly, Stallman has no problem with plain old C, which is covered by numerous patents by another convicted monopolist, AT&T. If his argument was ideologically sound, he would oppose C, C++, and every other popular programming language that FSF software is written in. In fact, he only opposes languages like Java and C#, which pose a credible threat to C/C++ popularity, which the FSF is heavily invested in, being that they hold copyright on a number of C/C++ tools. The success of C#, a technologically superior solution for many problems relative to C/C++, which is on equal legal footing with C/C++, which is being used in 100% free software stacks (GPL and MIT all the way down), to advance the cause of Linux on the desktop, is somehow bad and evil. This is absolutely absurd on its face, even from Stallman’s own purported ideological views.
Regardless of whether or not any specific patent licenses over ECMA 334 and 335 cover Mono’s implementation of those standards, if indeed such agreements are available (ITWire’s curlish “attempt” to secure such an arrangement aside), the fact that statements have been made in public supporting the idea of royalty-free licensing essentially reduces the financial impact of such infringement to zero. If Foocorp has a license to use patents, under a “non-discriminatory” license, and did not pay for them – then it would be discriminatory to change anyone else for them (breaking the signed terms regarding patent licensing), and as such, those patents lose any financial value. They may, however, still hold non-financial value (such as their use in defending against patent-related attacks), hence not making the patents “free for all” in any understood sense…
The layering of escape routes is extensive in Mono, especially Mono in Debian/Ubuntu. In the first instance, the contentious Microsoft-sourced non-ISO libraries such as System.Windows.Forms are not included by default, and are rarely used in Free applications anyway (because WinForms looks like ass, amongst other things). If a reason is found to remove these non-standardised libraries, then bam, they’re gone – without harming Free apps.
Stallman is using his prominent position in the Free Software world to spread totally unfounded FUD about a free software stack that is absolutely critical to the success of the free software movement. While Mono isn’t 100% GPL, it is 100% Free Software according to the FSF’s own definition. The patent claims Stallman makes vague reference to is nothing more than FUD. “Discourag[ing] people from writing software in C#”, as RMS advocates, is completely at odds with his own ideological positions on free software. The only possible downside is that Microsoft might get some good press, and the FSF would have to concede that Microsoft might have a few good ideas. This sort of Us vs. Them thinking has no place in a rational discussion, and it saddens me to see a once-great software leader now doing so much to destroy his own movement.