• NimDiagRender.exe is a renamed copy of nssm.exe (non-sucking service manager), it allows hosting other applications (such as Node) as Windows Services.
• node.exe: A copy of NodeJS that the Diagram Render Service uses to run its Rest API.
• Server.js: TIBCO source code for running the Rest API.
• screenshotter.js: TIBCO source code that creates diagram images.
• browserpool.js: TIBCO source code that controls a pool of Chromium instances that render the actual diagram.

If you do attempt to run any of these file individually nothing bad should happen, but you won't get any useful functionality either. If you run NimDiagRender.exe you will see a message about nssm and arguments needed to install a service using nssm.

Finally the only file that should be edited in the folder is '.env', this contains the configuration for the Render Service Rest API.

* To configure the Diagram Rendering Service you must configure the URL and port to use, this can be configured in the WebServer Config.ini Section below 

NimbusServices]
; URL for the Diagram Rendering service, including port number. E.g: http://<servername>:3000/ 
DiagramRenderServiceURL=http://mycomputer-name:3000/

** The default port can be changed if required but the port will need to be configured in the above config.ini and the Diagram Rendering Server .env file so they match 

.env file section 
############################################################################
# HTTP Settings #
############################################################################

# Allow the service to use HTTP protocol; 0 = Disabled; 1 = Enabled
NDR_HTTP=1

# The Port number on which the http service listens for requests
NDR_HTTP_PORT=3000