You can buy DD and BD via steam on the site of GOG.com, the last version 1.005A of DD. For BD I don't know which version it is on steam.

BD is a secuel (hope I spell it right?), not the second Divinity game wink



On 7th of february 2015 : I start a new adventure in the Divinity world of Original Sin,
it's a Fantastic Freaking Fabulous Funny ... it's my All Time Favorite One !