Is it possible in FME Server to run a workspace with workspacerunner that starts a workbench on another server in fme desktop? (and uses that license)

No, WorkspaceRunner will try and run FME Desktop on the same server (which I would not recommend). It's possible to use the FMEServerJobSubmitter to run a workspace on another FME Server (but not Desktop).

In theory, if you set up a webserver on the machine that runs FME Desktop and have FME Server call a page on that webserver that contains a bit of scripting (I've done it in the past with php but I assume it can be done in other scripting languages) that starts a local FME Desktop it should work. Or at least it used to work when I tried that a looooong time ago, I can think of a number of security concerns.

Can you tell us a bit more about your use case? Maybe there are other options...

thank you for your quick reply. Creating a webserver prob wont pass our security.

use case is that we get a lot of windows updates and i want to check if FME (Server & Desktops) is still working ok on miultiple servers. we have to test them manually at the moment. what we testing is to read some features from sde database and write them locally so we test both fme desktop and arcgis pro.

I figured that if could run them all from FME Server workspace on the click of a button.

The easiest solution will probably be to set up Windows Scheduled Tasks on the Desktop machines to run the test workspaces with FME Desktop.

thank you for your answer.

yes that is possible, but requires to log in on servers which i wanted to avoid. it is probably the next best thing!