Starting Saturday, July 12, the entire “South Park” library — 244 episodes in all — will be available for free on Hulu, and will continue to be free on SouthPark.cc.com (the address that is replacing SouthParkStudios.com) until Sept. 24. At that point, both Hulu and SouthPark.cc.com will have day-after-air access to new episodes from season 18. In addition, each of the sites will offer a revolving selection of 30 free episodes at any given time.
It sounds like they will not require Hulu plus until Sept 24, after that you will only get a "revolving selection of 30 free episodes" if you are not a member of Hulu Plus.
It's a shame really. I refuse to pay for Hulu Plus because of the obnoxious ads. I don't have cable for a reason, and that reason is I have a problem paying monthly for something and still being bombarded by advertisements.
For me I'll probably just stop watching South Park. Not that I would really watch it with any regularity, but it was nice to every once and a while pop over to their site and watch it free (but ad supported).