I don't know of a way to extract/convert the music. I don't have the PC version, though, so haven't really tried. Several people have mentioned recording the music in the background as the game was going, or finding various pieces on YouTube. A web search may turn up something.
There is a poll in the topic
Two new pieces from the Divinity II score!! to gauge the interest of a possible soundtrack...
There are 4 pieces of music on the D2:ED site's
media page, and more should evenyually be put on the
FoV site.
Kirill Pokrovsky has the Divine Divinity and Beyond Divinity soundtracks (and more) on his website in mp3 format, which is similar to the D2:ED music.