I DO NOT HAVE A CONURE----DISCLAIMER---
Does he always do that when perched? If so, I would suggest a vet just to be sure--he is moving his tongue enough that it is causing his tail to bob (which can be normal with that sort of movement) but it does seem a bit odd if it is happening all the time. It could be some sort of sexual/regurgitation thing if it happens only around certain people, but it would be best to verify...If he only does this when certain people are around, I would read it as a sexual invitation, like, "oh look at me, I like you and I am so nice....maybe this could lead to more?" If it IS only happening around you, I would encourage the rest of your family to strengthen their trust/bonds etc with him in an effort to avoid becoming his one and only!
My cockatoo does a bit of this when I pet her (like a "lovey" thing) or if she is trying to be sweet, but yours is really going to town lol--I just would double check if I were you..seems like it could be related to sex, but I am not certain.
