Well, but that forks only the Steemit website, not the Steem cryptocurrency behind it. The latter would be, as far as I know, a license infringement because Steem is not open source (it's "source-available" or "shared source", but it forbids you to create a clone with a new genesis block).

I have an idea of a re-implementation of a similar (but a bit different) content monetization scheme, based on an already existing coin. But it will take some time