As mentioned by the OP the repository once had an example that demonstrated the usage of SkeletonUtils.retarget(). It mapped an animated BVH skeleton to a different SEA3D skeleton.
https://rawcdn.githack.com/mrdoob/three.js/r105/examples/webgl_loader_sea3d_bvh_retarget.html
This seems to be the logic that is required for the OPs use case. It might be useful to replace the example with a new one using glTF and complete the documentation of SkeletonUtils.