As the GettingStarted documentation explains, the free NaturalONE Community Edition is meant for personal, non-commercial use only. It is a mostly full-functioning version of NaturalONE for use in a stand-alone PC environment. I believe Software AG considers connecting to a mainframe or LUW server as crossing the line into commercial use, so that feature is not supported. (Unless SAG is making some kind of workaround available to sites transitioning to Natural 9 and the Eclipse editor.)
Since your site has a Natural Development Server installed on the mainframe I assume your organization is moving to convert to using NaturalONE, so maybe you can get a commercial version installed by your DBA or tech support soon.
Hopefully the free demo version is useful to you in getting familiar with the Eclipse development environment. If you are new to Natural the full language is available to you to play with using the sample applications provided, or to write your own programs accessing the sample EMPLOYEES and VEHICLES files.
The NaturalONE Community Edition is provided for free for private, non-commercial usage. There is no support for the NaturalONE Community Edition.
The documentation that is delivered with the NaturalONE Community Edition describes all features which are available with the commercial version of NaturalONE. It describes, for example, the Natural Server view which is not available with the NaturalONE Community Edition. With the commercial version of NaturalONE, this view allows you to work directly on a Natural server and thus to download any existing libraries and objects to the Eclipse workspace. Since this view is not available with the NaturalONE Community Edition, it is also not possible to use, for example, the Predict Description and Generation component and the Natural Engineer component of NaturalONE. Please ignore the corresponding sections in the NaturalONE Community Edition documentation.
Please also ignore the installation description in the delivered NaturalONE documentation. To install the NaturalONE Community Edition, you have to proceed as described in “Installation”.