Jup, Valve ported the hl engine to linux and you can play both hl1 and cs1.6 on linux, now.
Phoronix: http://www.phoronix.com/scan.php?page=news_item&px=MTI4MzE
Steam DB: http://cdr.xpaw.ru/app/70/#section_history
reddit: http://www.reddit.com/r/linux_gaming/comments/178xsx/native_counterstrike_16_on_steam_for_linux/