Hi IrishBiker,
NoMachine is free to download and install for anyone who wants a remote desktop software for personal use. More info: https://knowledgebase.nomachine.com/AR03P00972
The free version installed on the host accepts one connection at any time. A user can have NoMachine player (the client side) installed on as many devices as they want. However, if you try to connect from 2 or more at the same time to a host with the free version installed, it won’t be possible. Only one connection will be possible.
The Enterprise Desktop commercial version, on the other hand, will accept multiple simultaneous connections. If you have many devices which want to connect to the same host at the same time, then Enterprise Desktop is what should be installed on the host.
From your description, the free version will probably suffice. You can in any case compare the two here: https://www.nomachine.com/remote-access-for-everyone.