At present time, the site is still in its beta stage and plans state clear that it will be ad-supported:

"One goal in moving forward is to make every episode of ‘South Park’ available world-wide. Currently, full episodes are not available in the UK, Australia and a few other foreign territories but we’re not far off from making that happen. We have some contractual issues to sift through but we’re getting there," said Anne Garefino, General Manager of South Park Digital Studios,

The new episodes will get special treatment, as they will be available only one week “soon after” the original broadcasting. No worries, they will return to the site after 30 days.

Show creators Trey Parker and Matt Stone said that the idea of putting South Park online came to them as a personal necessity:

"We got really sick of having to download our own show illegally all the time so we gave ourselves a legal alternative."

It would be interesting to see which shows are to take the same road.