It was actually a guy at Warthog who was promising the mission editor, he said it was something he was developing on his own free time. I'm not sure how much time he actually put into it...doesn't really matter now.
Why collect ultramarines when theres dark angels out there. Espescially deathwing. Whats that big secret the deathwing is guarding anyway. (All my WH 40K experience is from the first space hulk computer game, dawn of war and the tabletop game's webpage, but i still love that universe.)