Half-Life.org have interviewed Neil Manke and Einar Saukas (makers of They Hunger) from Underworld: Bloodline

Dabaz: Approximately how long did you have to keep this project under wraps?
Neil Manke/Einar Saukas: We kept this project secret for the entire development cycle (a couple months), right up until the release day.
John Callaham at HomeLan Fed kept on our toes most of the time, asking for information on our secret project, which is the reason he scored the first interview with us right after the release (the squeaky wheel gets the grease).

To read more of this interview head on over to Half-Life.org

Here's some pics: