how do we get yaw, roll, pitch from POSIT rotation matrix

edit

You can use the c implementation, it still works. You can also use solvePnP, which seems to replace cvPOSIT for pose estimation.

Pedro Martins in his Master's thesis explain what you want with cvPOSIT :

http://www2.isr.uc.pt/~pedromartins/Publications/pmartins_MScThesis.pdf

And here with solvePnP :

http://www.morethantechnical.com/2012/10/17/head-pose-estimation-with-opencv-opengl-revisited-w-code/

Basically the cvPOSIT is not a function provided by the openCV library as can be seen here. I am guessing you are using some kind of wrapper functionality provided by another development group. Please go to the specific wrapper or add-on library webpage.