Comment 2 for bug 70651

It may indeed be FUD (and Microsoft is certainly known for doing that, ne?) but there may in fact be actual patents involved and so this really needs to be evaluated in detail by someone who has a legal background, but that's not me :)

http://en.wikipedia.org/wiki/Microsoft_.NET_Framework

"While Microsoft and their partners hold patents for CLI and C#, ECMA and ISO requires that all patents essential to implementation be made available under "reasonable and non-discriminatory (RAND) terms." In addition to meeting these terms, the companies have agreed to make the patents available royalty-free. However, this does not apply for the part of the .NET Framework which is not covered by the ECMA/ISO standard, which includes Windows Forms, ADO.NET, and ASP.NET. Patents that Microsoft holds in these areas may deter non-Microsoft implementations of the full framework."

but... see the URL in the first post regarding RAND. Then:

http://en.wikipedia.org/wiki/Mono_%28software%29#Mono_and_Microsoft.27s_patents

"Mono's implementation of those components of the .NET stack not submitted to the ECMA for standardization was the source of patent violation concerns for much of the life of the project. In particular, discussion has taken place about whether Microsoft could destroy the Mono project through patent suits. The problematic parts are not the core technologies submitted to the ECMA or the Unix/Gnome-specific parts. The patent concerns primarily relate to technologies developed by Microsoft on top of the .NET Framework, such as ASP.NET, ADO.NET and Windows Forms, i.e. parts composing Mono's Windows compatibility stack. These technologies are today not fully implemented in Mono and not required for developing Mono-applications. Not providing a patented capability would weaken the interoperability, but it would still provide the free software / open source software community with good development tools, which is the primary reason for developing Mono. However, on November 2, 2006, Microsoft and Novell announced a joint agreement whereby Microsoft agreed to not sue Novell or its customers for patent infringement. According to a statement on the blog of Mono project leader Miguel de Icaza, this agreement extends to Mono but only for Novell developers and users."

Miguel de Icaza's blog post in question is here:
http://tirania.org/blog/archive/2006/Nov-04.html

He states "I do not know of any patents which Mono infringes."

The problem is that patents are like landmines; if Microsoft believes one or more of its patents are being infringed upon by Mono, companies who decide to use Ubuntu could be in trouble if MS wanted to make an example of them by suing.

IMHO it would be in everyone's best interest to move away from MS-based technologies (e.g. Mono) and towards ones where we know that patents aren't an issue (e.g. Java).