I don't know how news like this is normally reported here, but I thought a blog would be a practical way.
The first episode of season 6, "Wake Up / Escape From the Citadel", is available for free on iTunes.https://itunes.apple.com/us/tv-season/adventure-time-vol.-7/id850454475
These two episodes aired yesterday, but I did not look at iTunes until today. I do not know how long the episode will be available for free.
- Adventure Time, Vol. 7 on iTunes (archived page; retrieved April 23, 2014)