I installed this ROM yesterday and was just able to install Spotify from the market. I opened it and signed in ok, it then informed my I don't have premium so can't use spotify mobile.
I also noticed this on the spotify website, note sure if it helps.
* Having problems installing from the Market? If so, from your Android phone, go to Settings > Applications and check the box called Unknown sources. Then, using the phone’s browser, go to m.spotify.com and use the option manual install. Hope that does the trick.