Yes, it's legit, and there's lots of different ways of doing it. It sounds like you are asking about how to get satellite to computer... if that's the case a dvb card or usb thingy like the usb world box is probably needed...
Another route, if you just want to use computer to record stuff to later burn to dvd, you could just hook coax from vcr or ota or even tv out of an fta receiver to computer via graphics card with tv in... my all in wonder does that sort of stuff...
There's other technology too... slingbox... etc.
The stuff that may or may not be illegal is the p2p stuff... it's a bit of a grey legal area... That stuff requires you not having a satellite dish, just internet connection and you pull in signals from other people's tv's since they are putting it online for others like you to see... and even that's legal, so long as they are using stuff they have the copyrights to... it's when they don't have the copyright and are doing that sort of stuff things get illegal at times...
Also, decrypting pay tv is illegal unless you are legally paying to do so... doesn't matter if the signals are coming in through fta box, usb, pci, or any other ways...
All of that said, I'm no lawyer, so what do I know.