There are third party projects such as FreeNX and NeatX which can be considered "derivative" open source versions of the NX 3.x server software suite. These are not produced by NoMachine developers.

In general, independent implementations are set to be compatible as they use the same underlying core components released by NoMachine under the GPL license. However, NoMachine can't ensure that all functions offered by NoMachine NX are compatible implementations or that the way these functions are implemented allows for complete interoperability. We therefore recommend all our customers and users to uninstall the FreeNX  or NeatX installation if they are considering installing and using NoMachine NX.

There is no direct or indirect connection between the FreeNX or NeatX projects and NoMachine, and NoMachine doesn't directly support either of the projects. For any support question or enquiry related to the interoperability between these and NoMachine, you should contact the appropriate developers, by posting your questions on their public mailing lists.