I'm not 'judging' you, as I assume that if you really just wanted to pirate it, you wouldn't be asking here.
You *can* still find the game in some places - I see it in the bargain game areas at various stores all the time (like EBGames). Sometimes it is the JK/MotS pack, sometimes just JK.
You can also get it from Amazon
http://www.amazon.com/exec/obidos/tg/detail/-/B00000K50S/qid=1081768207/sr=1-5/ref=sr_1_5/102-6095535-5225726?v=glance&s=videogames)
When I checked, there were 8 'z-shop' sites available, 5 new and 3 used, and only one was just JK.
Also, there is eBay - a quick search (jedi knight dark forces as keywords) gave me ~20 hits, all JK.
So you *can* still buy it, and I hope you get it and enjoy a truly classic game.
BTW - you posted this in the Dark Forces, not Jedi Knight, forum.
Mike