PJSIP has not yet released there Android version, it is only for testing purposes. You can find the PJSIP projest for android in branches. Here is the link : http://svn.pjsip.org/repos/pjproject/branches/projects/android/
So I would suggest you to download the whole pjproject.
You can find the apjsua in pjproject/branches/projects/android/pjsip-apps/src/apjsua