Not that I'm aware of. But if you're familiar with normal skybox rendering, then this is just a minor modification. You would follow the GI cache use instructions here to generate the GI caches:
http://planetside.co.uk/wiki/index.php?title=Terragen_4_Global_Illumination#Rendering_with_GI_cache_filesRemember, 1 cache for each of the cube faces (and these *all* need to be generated before final rendering of *any* cube face). They should be created with file names incorporating a number corresponding to the cube face, e.g. cubeface_0001.gic, cubeface_0002.gic, etc.
Then when you render, either use a GI cache loading name that incorporates an appropriate sequence wildcard (e.g. %04d), or if this doesn't make sense to you, I believe if you specify just the 1st file and set the rest correctly, it should auto-load. So the number of files to blend should be set to 6, equal to the number of cube faces (and the number of GI cache files, of course), and then use "Equal Blend Within Range".
Also don't forget to turn off motion blur when rendering cube faces, at least if you are animating the camera to achieve the 6 views (you can also do this manually).
As an alternative to all that you *could* try GI Prepass padding, however it's not guaranteed this will work as well as the cache-based method.
Honestly generating sphericals is much, much simpler.
Maybe you can just convert a spherical image to a cube map with 3rd party software?
- Oshyan
