Hi, when Forest is running in a render node, it doesn't require any license.
The setup program includes a specific option for render nodes, but it's basically a standard installation without specifying any license mode.
Usually these problems are caused because the plugin is not installed correctly in the render nodes, or cannot run for some reason.
Does it happen only with Distributed Rendering, or also with Backburner ?
Have you tried rendering a basic model (as a scattered teapot) ? Just to be sure it's not a missing texture issue...