more simply...you don't need a cablecard if you just want ABC, NBC, CBS, FOX, CW, PBS, WB other broadcast channels. just a standard PC tuner will pull those channels. even if you are paying for expanded channels, and other TVs plugged into the wall get them, through a PC only these channels appear and work (the "Broadcast" channels).
any expanded channels like ESPN/FX/TNT/Discovery etc require the Cable Card and CC tuner to tune them in.
WMC is required if you want to use the Cable Card. really not too many great ways around that. and probably is still the best for liveTV/DVR if you want to keep it simple.