OK, I'm a bit confused. This site, studentagencybus.com, seems to be one step removed from the official Student Agency site (studentagency.cz, or studentagency.eu for English or German), which facilitates direct reservations, knows whether your bus is full or not, and allows you to purchase tickets without having to wait 24 hours for confirmation. Their prices are, strangely, posted in Hungarian forint.
The official site so far doesn't know about the airport bus to Cesky Krumlov. I'm sending an email to the official site asking about this other site, and whether this new bus from the airport is planned.
Update: Student Agency replies that they don't offer such a bus. I can't seem to get the blockquote feature working but I've reproduced the email below as best I can.
thank you for your interest in our services.
We do have busses to Cesky Krumlov, but it´s not a direct route. You´ll need to switch busses and get from one stop in Prague to another (Praha Florenc - Praha, Na Knížecí).
- Praha, Letiště Václava Havla -> Praha, ÚAN Florenc
- Praha, Na Knížecí -> Český Krumlov, AN
You can buy our tickets here in CZK or here in Euros.
operátor call centra