The Free Software Foundation has published a reply to Microsoft’s Community Promise surrounding C# and CLI. Here’s a snippet:
The ECMA 334 and 335 specifications describe the core C# language, including information about standard libraries that must be available in any compliant implementation. However, there are several libraries that are included with Mono, and commonly used by applications like Tomboy, that are not required by the standard. And just to be clear, 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.
Microsoft needs to do more to assure the free software community that they will not sue over the use of .NET. Release an irrevocable license for all patents in .NET (or at least Mono’s implementation) that remains in effect even after a sale of said patents. Or make a deal with Novell and get them to release Mono under GPLv3..