see release notes on mojoportal.com http://www.mojoportal.com/mojoportal-2393-released
Note that we have separate deployment packages for .NET 3.5 and .NET 4.0, but we recommend you to use .NET 4, we will probably drop support for .NET 3.5 once .NET 4.5 is available
The deployment package downloads on this page are pre-compiled and ready for production deployment, they contain no C# source code and are not intended for use in Visual Studio.
To download the source code see getting the latest source code using TortoiseHG
I don't recommend downloading the source code from the source code tab here on codeplex, when people do that they often report weird things not working correctly, its best to get the source code using TortoiseHG.