>> https://languagetool.org/download/LanguageTool-stable.zip
> 
> It appears to be designed as a full-blown, multi-connection server.  
> Even if it is restricted to a local address, if it were a multi-user 
> machine I'd be concerned about whether other users might gain access to 
> the text I've sent to the server for processing.
>

The zip file above contains the three versions of the program: GUI, 
client-server, and command-line.