Hi,
Well, its problematic to develop against the pre-compiled release files because mojoPortal is built around the VS Web Application Project type and opening the pre-compiled package in VS as if it were a Web Site Project instead just doesn't work right.
If you want to run mojoPortal in Visual Studio you really are better off doing it using the source code which includes the .csproj files.
Also for almost anything you want to develop yourself there are lots of example code to do similar things in mojoPortal, so its an advantage to work directly with the source code. It also helps you understand how mojoPortal works. The source code is the most up to date and accurate documentation.
Hope it helps,
Joe