There is no legal issue, this is a fork. A fork is a split of the chain, and all previous data (before the launch) carries over. This is quite normal.
Yes starting from scratch to build a whole new chain is/was a possibility and anyone can do that at any time. I would say that wasn’t an option in their specific case, but hey maybe some are experimenting with that options.
That’s the great thing about open source technology- anyone can build, contribute and experiment.