Matthias,
We also have strange inconsistencies you mention...
I'm fairly certain that during our early tests the we also needed the FUSION_LICENSE_SERVER variable to point to the Fusion Server service / Dongle machine, but later tests worked without the variable.
Also, our other tests needed the Fusion Server service to be installed on a machine in order to discover a dongle on the network. Then we uninstall the service, and even reboot that machine, and the RenderNode continues to get a license.
I'm sure there is some kind of logic behind these inconsistencies, but we have yet to figure it out
