The Free Software Foundation (FSF) doesn’t like Microsoft, doesn’t like software patents, it especially doesn’t like Microsoft’s patents, and it doesn’t trust the two of them in the same room together.

It’s convinced that Microsoft is eventually going to sue any open source developer who uses Mono, the Novell-supported open source version of Microsoft’s .NET widgetry, or who writes open source programs in C#, the Microsoft development language.

It’s warning off developers now because Microsoft has added both C# and Mono – or rather the ECMA 334 and 335 standards that embrace them – to its two-year-old irrevocable, legally binding Community Promise not to sue. (See www.microsoft.com/interop/cp/default.mspx.)

The Free Software Foundation is sure Microsoft means to gull open source developers into a false sense of security and then snap the lid down on their typing fingers.

It suggests that Microsoft has a secret cache of patents tucked away to attack the unwary.

“Using patents to divide and conquer the free software community is a fundamental part of [Microsoft’s] corporate strategy,” it says.

“Because of that, C# represents a unique threat to us. The language was developed inside Microsoft, so it’s likely they have many patents to cover different aspects of its implementation. That would make free software implementations of C#, like Mono, an easy target for attack.”

FSF president and resident paranoid Richard Stallman is alarmed – or maybe it’s that he feels his grip slackening – because of “Debian’s decision to include Mono in its principal way of installing Gnome, for the sake of Tomboy which is an application written in C#.”

He claims it “leads the community in a risky direction. It is dangerous to depend on C#, so we need to discourage its use.”

“The problem,” he says, “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. (See http://swpat.org and http://progfree.org.) This is a serious danger, and only fools would ignore it until the day it actually happens. We need to take precautions now to protect ourselves from this future danger.”

According to the FSF, whose goal is to get Microsoft to foreswear its IP completely, Microsoft’s promise, is “full of loopholes.”

See, Microsoft’s promise only covers implementations “that are compliant with all of the required parts of the mandatory provisions” of a covered specification. So FSF reasons that because Mono and applications like Tomboy use libraries that aren’t required by the ECMA 334 and 335 specifications they’re swimming in crocodile-infested waters with their pants around their knees.

“And just to be clear,” it says, “we’re not talking about Windows-specific libraries like ASP.NET and Windows Forms. Instead, we’re talking about libraries under the System namespace that provide common functionality programmers expect in modern programming languages: binary object serialization, regular expressions, XPath and XSLT, and more.

“Because these libraries are not defined in the ECMA specifications, they are not protected in any way by Microsoft’s Community Promise. If this were the only problem with the promise, it might be safe to use applications that avoid these libraries, and stick to what’s in the standard. But even the code that’s covered by the promise isn’t completely safe.

“The Community Promise only extends to claims in Microsoft patents that are necessary to implement the covered specifications. Judging just by the size of its patent portfolio, it’s likely that Microsoft holds patents which a complete standard implementation probably infringes even if it’s not strictly necessary – maybe the patent covers a straightforward speed optimization, or some common way of performing some task. The Community Promise doesn’t say anything about these patents, and so Microsoft can still use them to threaten standard implementations.

“The Community Promise does nothing to change any of this. Microsoft had an opportunity to take action and demonstrate that it meant us no harm with C#. Instead, they took meaningless half-measures that leave them with plenty of opportunities to hurt us.”

ECMA 334 describes C# and ECMA 335 defines the Common Language Infrastructure (CLI) in which applications written in multiple high-level languages can be executed in different system environments without having to rewrite those applications to take into consideration the unique characteristics of those environments.