Most of IOTA is open source, and the parts that are not (like the Coordinator) can be implemented by interesting parties themselves (no guarantee that their Coordinator is on par with IOTA's, though).
Therefore, it can be forked, and it has already happened.
The fork was without forking the ledger (like Litecoin is a fork of Bitcoin), so IOTA holders did not get another cryptocurrency for free. But it would also possible to include the latest snapshot in the fork.
When you see their tangle explorer, it looks very similar to IOTA's, just that they call the tangle a mesh in the extend that they also have a "Lastest Solid Submesh Milestone".
Apart from that, they are not very successful (not in the top 1000 on coinmarketcap).
Question is: Why would anyone want that? IOTA is still pretty beta, and every fix made by the IOTA foundation would have to be redone by the forkers.