The new free NoMachine can be used as a client to get access to your NoMachine NX server. You can just disable server access if you wish to use it as a client software only (see the tutorial here to do that: https://www.nomachine.com/how-to-disable-access-to-the-local-desktop).
Version 3 is a 10+ year-old product and old products are replaced everyday. For every old product replaced there are those that had learned to live with it and want to “hang on to it”. So I am interested in knowing if there is anything special that makes you prefer client 3. I think most of the problems are due to communication problems. These communication problems are somehow normal when you have to deal with a large user base and with a completely new market space at the same time (Windows and Mac users). For example, people that used client 3 are confused by the fact the new free version is also a server. These people may have overlooked the fact they can install the free Enterprise client. This is a standalone client as it was the old client 3.