The editor is open-source, and it being open-source is great. Others can contribute, it generally helps adoption, it will probably help with getting people to author plugins, and it means if they go in an undesirable way, the community will be able to fork.
So without making it non-open-source, they’d need to do open-core, which is incredibly hard to pull off, as you usually end up cannibalizing features in the open-source version (even if you have contributors willing to contribute them, you block it to not sabotage your revenue stream).