Avastar provides an animation mapper that allows to map foreign armatures to Avastar rigs as long as the armatures are compatible. By default Avastar expects rigs with a T-Restpose. However, the condition for a successful import is actually:
The imported animation must use the same restpose as the Avastar character
So, if you convert your Avastar rig to a compatible restpose, then you can import and map any animation
Section sub pages
Motion Transfer Tools The Motion Transfer Tools are designed to transfer the Animation of an imported BVH file to an Avastar rig. So you will typically first create an Avastar character (the Target), then import the Animation, map it to Avastar, and finally transfer the Motion to the Avastar Timelin...