Yes, it is possible to get legal FTA satellite TV on your PC. Some people build a PC just for this purpose, HTPC (Home Theater PC). Myself, I bought a Nexus-S card a few years back and unsuccessfully got it to work. But after reading many postings here and posting a few myself, I have had great luck since. I only use my Nexus-S to bring in the FTA music on 119. But bought a Fortec Lifetime Classic NA receiver for my TV and have a second dish pointed to Galaxy 10R. The main thing I noticed was circular (119) is not receivable by Ku (123) LNBs. I think that is the biggest hurdle people run into at first. I personally am satisfied with my setup. It's very basic, but it uses my old Dish Network dish and old DirecWay dish. So the only hardware I have purchased was the Fortec receiver, Nexus-S PCI card and a SF-95 satellite finder.
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.
At the top of this forum section, there is a subsection called Free to Air PC DVB Discussion.
Check up there for more info on PCI cards and USB boxes that hook to your computer, a satellite dish, and receive the standard FTA signals everyone is talking about.
FTAlist has a nice list broken down by language. Global has a similar list organized a bit differently.
Both are good, and will get you an overview quicker than digging through Lyngsat web pages.
Most cards/boxes come with software to receive and record.
If your goal is more to watch than to record, a regular stand-alone FTA receiver might be a better idea.
If you go with a PCI card or USB box, you can watch TV on your compter, but it may take a bit more effort to hook your computer to the TV set.