For a bit of incompatibility, there are some 'specialized' projects as following:

MsgPack.sln: Visual Studio solution file for .NET Framework build.

MsgPack.csproj: Project for full CLR (.NET 4 Client Profile)

MsgPack.Net35.csproj: Project for full CLR (.NET 3.5)

MsgPack.WinRT.csproj: Project for WinRT compatible .NET lib. (experimental)

MsgPack.Silverlight.4.csproj: Project for Silverlight4, contains only core (manual) packing/unpacking.

MsgPack.Silverlight.Serialization.4.csproj: Project for Silverlight4, contains typed serializers and their infrastructures.

MsgPack.Silverlight.5.csproj: Project for Silverlight5, it is similar to MsgPack.Silverlight.4.csproj.

MsgPack.Silverlight.Serialization.5.csproj: Project for Silverlight5, it is similar to MsgPack.Silverlight.Serialization.4.csproj.

MsgPack.WindowsPhone.7.1.csproj: Project for Windows Phone 7.1, it is similar to MsgPack.Silverlight.4.csproj.

MsgPack.WindowsPhone.7.1.Serialization.csproj: Project for Windows Phone 7.1, it is similar to MsgPack.Silverlight.Serialization.4.csproj.

MsgPack.mono.sln: Mono Develop solution file for mono build (mono does not support client profile, and recent Silverlight assemblies).

MsgPack.Mono.csproj: Project for mono (.NET 4 Full Profile)

MsgPack.UnitTest.Mono.csproj: Unit test for MsgPack.Mono.csproj, it is mirror of MsgPack.UnitTest.csproj project.