Bluefox91: The Rights are currently owned by Warner Brothers, of all companies.
I know Monolith's webpage states "BLOOD™ Warner Bros. Entertainment Inc.", but if you go and do a TM search at uspto.gov, you will find that the TM for Blood was canceled on October 24, 2009. I'd provide a link, but the search results are generated per person. If you search for the Registration Number: 2233394, you will find it.
Atari still has publishing rights to Blood & Blood II, else GoG.com wouldn't be able to sell it.
I'm confused about who actually owns the back story to Blood. Whether Monolith sold all rights to the Blood franchise to GT Interactive, which was the transferred through acquisition to Atari, or of Monolith held on to the background (similar to what happened with FEAR) which WB got when they bought Monolith back in 2004.
I use to worry about what might happen to Blood if WB got their hands on it, but the TV series "Supernatural" is pretty awesome, so it certainly could be done right.