You need to make your own travel arrangements.
You should fly into Adi Sucipto Airport in Yogyakarta, which is 7 km from the Gadjah Mada University (UGM) where the summer school will be held.
Getting from the airport:
Rajawali taxis are the official airport taxis and these are the ones that you should use - others could end up costing you much more! You will find the Rajawali taxis on the Arrivals level at the airport. Buy a fixed-price taxi coupon from the Transportation counter (about 60000-110000 IDR (7-10 USD), depending on where you are going to). Then go outside to the taxi stand. It will take 30-35 minutes to the accommodation options near UGM.
Trans Yogyakarta bus costs less than 50 cents US, but it takes about 45-60 minutes and you will need to find out which bus stop is closest to your accommodation.