Good news. But this will just help Mijin make money, as they're offering a 30 day free trial, then charging $0.65 per hour. How will it benefit the NEM public chain?
The benefits are indirect, similar to Ethereum Enterprise Alliance. It is also good publicity, and developers learning your ecosystem.
And it will be easier for enterprises to use the Mijin private chain to host the necessary nodes to run the network. That is really great because every project on mijin indirectly helps the ecosystem in some part
Even though the code base is shared, the nodes are not shared. The private network that Mijin facilitates runs its own nodes, which transact based on their needs. They do not host or relay public NEM transactions and are therefore not NEM nodes.