The graphene blockchain code is open source and can easily be copied. At least one if not more than one other blockchain has been launched since Steem using that code. Moreover there are other blockchains out there that are close enough (for example lisk has 10 second blocks).

Furthermore 'secret' doesn't apply since the methods being used are all public and can be copied if there were a demand for it (the aforementioned Lisk being an example of something using similar methods)