There are other cryptocurrency networks similar to bitcoin--even some that claim to be bitcoin--but there is only one bitcoin (BTC).
Like any open-source software, the bitcoin protocol can be copied and modified. There are some modified copies of bitcoin that exist as forks of bitcoin. There are other cryptocurrency blockchains that have been made with entirely new code. But there is one thing you can't duplicate, and that's the robust computer network devoted to mining and securing bitcoin.
