I have been told that it is not safe to use saltwater driftwood in a freshwater tank, however I have read of people using it safely also. If you want to try it then I would suggest boiling the crap out of the wood then let the wood soak for a good long time to get as much salt as possible out.
If I got sea driftwood, I would
1) soak the wood for a week or two
2) drain and re-soak...add a couple bottles of 3% Hydrogen peroxide..let soak 1 day
3) drain and dose a fair amount dechlor (the ones that handle heavy metals etc)...soak and drain the next day.