Here is a thread by someone who has integrated GSP into DNN. However, there is not a module for DNN that plugs in nicely.

I am currently considering making a version of GSP as a DNN module. In fact, just today I downloaded DNN and started reading through the "how to make a module" document.

Modules in DNN are pretty easy to do. Your forum works in DNN (I've done it in the past) very easily. Should be a snap to provide a module that incorporates GSP into DNN while still maintains its original function and installation.