I can't seem to find anywhere on the Internet about iClone's very strange Bones/Joint rigging, making not attritive to use with other 3D applications where animation is retargeted (exporting FBX or BVH"). Here's my list:
1. The biggest issue is the bones not have a common "up-vector" or in other words, the bones axis are not the same. In the middle body, "z" points up, legs, point down, feet point back. No matter what app I load an iClone file (Cinema 4D, Blender, DAZ 3D, Autodesk SDK, the axis are not same.
2. There's no logic to the rigging rotational values. You should be able to zero out all bone rotations and get a default pose (like a "T" or "A"). If you zero an iClone figure you get a mess. You can't simply export it in a standard pose and then zero the rotations because the values are so far from zero you get gimble oscillations.  I'm guessing Motion Builder users are having the bone rig, re-rigged, because files I've used that have come from Motion Builder are not like iClone files.

I started to write some Python code to try to fix the bone 3D rotational matrix math, but after going through two up-vector changes had had to stop and ask why am I the only one seeing this mess?