I think the team that drafts him would have to buy out the final year of his current contract, if I remember correctly.
Stitches or someone would probably know for sure.
His situation is a bit weird and I don't know exactly what the terms of his contract are. He has 7 year contract(4 more years after this summer), but according to different sources he either has a player option on his contract this summer, or not. I don't know which one it is(from what I've read it seems like he does have player option and he will be able to join right away without us paying anything). If he doesn't have the player option, the buy-out clause would be 2M euro(2.3M USD)