Automate unDRM and DecryptIt are GUIs for drmdbg and drm2wmv. As for FairUse4WM, I don't really think it is just a GUI for these programs.

I haven't seen any sources for DRM removal software, except for the old freeme.exe that must be of no help here.

FairUse4WM was developed by doom9 member called Viodentia. He hasn't visited the doom9 forum for a while. Also he hasn't released the source codes of FairUse4WM publicly. The source codes could be analyzed by the M$ developers so they can make patches easily. That is why they are not and shouldn't be available to the public.

Here are some doom9 members that released fixes for the FairUse4WM:
Divine Tao, Monkey Boy, milOtis. I don't think they had any access to the source codes.

Also mayong has posted lots of interesting info about drmdbg so he might know more about DRM removal than many of us.