Mono implements the 2 ECMA standards related to the C# language, the CLR and the core of the .NET library, plus Microsoft-specific APIs which are not covered by the ECMA standard.
The ECMA standards are distributed under RAND terms. This is not enough to guarantee a free implementation, however Microsoft issued a statement under the Community Promise that these standards are worry-free of patents as long as the implementation implements the whole standard (which is quite light and contrary to Java, supersets are allowed).
What can be attacked are implementations of components, like ASP.NET, ADO.NET, Windows.Forms and maybe Silverlight. However, this would be a hard thing to do, simply because Microsoft ended up cooperating with the Mono team on at least the implementation of Silverlight. And also they actively encouraged Mono by other things, like referring to Mono in their official docs, which means Estoppel applies: http://en.wikipedia.org/wiki/Estoppel
So quite the contrary, I think Mono is even safer than Java, as Java is not governed by a real standards body and you can't implement Java unless Oracle allows you to (hence Harmony is dead). Even forking OpenJDK may be problematic, as the implicit patents grant may not apply to derivate works (at least in Europe).
The ECMA standards are distributed under RAND terms. This is not enough to guarantee a free implementation, however Microsoft issued a statement under the Community Promise that these standards are worry-free of patents as long as the implementation implements the whole standard (which is quite light and contrary to Java, supersets are allowed).
What can be attacked are implementations of components, like ASP.NET, ADO.NET, Windows.Forms and maybe Silverlight. However, this would be a hard thing to do, simply because Microsoft ended up cooperating with the Mono team on at least the implementation of Silverlight. And also they actively encouraged Mono by other things, like referring to Mono in their official docs, which means Estoppel applies: http://en.wikipedia.org/wiki/Estoppel
So quite the contrary, I think Mono is even safer than Java, as Java is not governed by a real standards body and you can't implement Java unless Oracle allows you to (hence Harmony is dead). Even forking OpenJDK may be problematic, as the implicit patents grant may not apply to derivate works (at least in Europe).