I know this is an old post, but thought it was pertinent to add it on here, if it is not already known, but happen to come across this recent article stating that Blackmagic has released a Linux SDKs for their DeckLink, Multibridge and Intensity lines. (Including both a Software Driver and SDK that they say can be downloaded from their site)
The Blackmagic Design article can be found here:
http://www.blackmagic-design.com/press/detail.asp?pressID=165
Hope this helps, that is, unless this isn't already known on here.
Best,
-James-
James G.
Upstate NY, USA
3.0 GHz Quad Mac Pro
4 GB Ram,
1 TB RAID Offline Media Drive
4 TB RAID Online Media Drive
FCP 6.0.5
Blackmagic Decklink HD Extreme