My rule is to use it if it can be flattened with no more than moderate hand pressure. Dovetails in particular are forgiving, because the joinery forces pieces into contact along the entire joint line. The wood will continue to move over time anyway. Also, just by looking at the ring orientation, these pieces are going to bend that way.
You'll want to be careful with layout - best to clamp the boards flat, so that when you mark across the thickness (ie, on the end grain for tails, presuming tails-first) you are marking square across. If you're using a machine jig, make sure they are clamped in with enough pressure to stay flat during machining.
Finally, perhaps most importantly, orient the boards in the joint so that the ends will tend to cup into the joint. Oriented the other way, the ends will eventually show gaps. As i mentioned above, the joinery itself will keep the middle part tight. This means that heart side should face out of your box/drawer/assembly.