Is the OST included?

No, it is not, sadly. Getting the OST for this game is probably way too costly, hence why they don't bother adding it, I guess. Maybe it will be purchasable later on Bandcamp or Double Fine's store.

The Gone Jackals Bone to Pick album is available on itunes.

And the game's soundtrack by Peter McConnell can be played in the game's very own jukebox (in the bonus menu)

Just use DoubleFine explorer and extract the 320 kbps MP3s from the game's "full.data" file.