The 1.2 version of the tool is now available. Please read the release notes rather carefully, it is rough around the edges and it will misbehave if not treated in certain ways, I'm afraid. Java 8 or higher is required to be installed.
For you specifically, you want the file "Pool of Radiance/data/Anims/Objects/spnspire.nat", which is the Spinning Spire/Stone. You can open that file in the GUI and export it as Wavefront obj file, which should be importable and usable by every 3D software that is around (I've only tested Blender, though).
The model support is limited to "static" models, like the Spinning Spire, I haven't figured out how the "animated" (character) models work so far. I'm working a write-up again which I will publish in some time.