Generally using wood found isnt a good idea with all the diseases/pests it could introduce to your tank, but with common sense it can happen.
As far as i know the only real rules to using your own
driftwood is:
make sure the wood is LONG dead, it has to be completely dead- that wood looks pretty dead to me and should be safe in that instance
You must soak the wood for many weeks, sometimes months. Wood releases tannins over time that will discolor the water you keep it to soak. I would soak it for atleast a month.
With that piece of wood coming from the river basin (actually, ANY piece of wood for that matter), I would soak in boiling water. Wether you soak that in a 5 gal. bucket, or a tank (depending on if it'll fit in the bucket or not, obviously), wherever you place it to soak boiling water on your stove and dump it in your bucket/tank. The boiling hot water will kill anything on the wood. After a month of soaking (with occasional water changes as the water discolors), the wood would be definately safe to use!