I’m not sure but there might be some confusion here still.
According to the PhysX docs (https://developer.nvidia.com/sites/default/files/akamai/physx/Manual/Joints.html) the formula you mentioned is for linear drives. For angular drives “damping - applied to the drive spring (used to smooth out oscillations about the drive target)”.
While it is weird that one time damping is related to velocity then to spring, it does make sense to have a parameter to tweak oscillation.
And yes, “0 = INF” is bad usability, I should have remembered that one from UDK times… Maybe under the hood you could replace 0 with 0.000001 or something when feeding PhysX and let the user just type in 999999 for very big forces.
And while we are at it, I’m not sure if it still works like that but back in the day there were some nasty, undocumented value processing like where one could not have a swing/twist limit angle less than 5 degrees or where spring/damping value of 0.1 was rounded to 0. It would be great not to have those this time around. 
Thanks for looking into it.