The .NET framework is the one providing interoperability between 32-bit and 64-bit platforms. This means that any application that is coded with 100% managed code can be compiled either in 32-bit or in 64-bit. The grid is 100% managed, so it can be compiled for either platform.
Actually, if you set the platform target of your application to "AnyCPU", it will run as a 32-bit application on a 32-bit OS, and as a 64-bit application on a 64-bit system, which means you can develop an application that is compatible and fully 32-bit or 64-bit, depending on the system it is running on, without the need to recompile the application for each system.
You will find the platform target on the Build tab of the project properties.
Xceed Software Inc.