DLC has gone way out of hand if it goes deep into PC Gaming. DLC on PC games traditionally mean it's free, unless its an expansion pack such as Opposing Forces/Blue Shift ect. DLC as we see on the consoles is practically non-existent as most of the mods and extra stuff are either provided freely by mod communities or by the creators (usually as fixes or enhancements).
Unless a website can not provide bandwidth to host content such as mods/maps there wouldn't be any restrictions to using bitorrent technology or even websites dedicated to hosting files like Mediafire. Certain servers usually give out addresses to the owners website, especially communities dedicated to the game. They usually have servers provide the content by having you download them as you try to enter a server.
With all that taken away, you may as well go play on your 360/PS3 as it's the same thing only restricted and worse.