I contacted the seller of the Bullet Proof Security WP plugin. He said someone asked him about the use of the domain mapping plugin regarding the free version of BPS >>> http://wordpress.org/support/topic/is-bulletproof-security-compatible-with-multisite-mode
He never replied with a confirmation that the domain mapping worked or if there were issues.
He said that If domain mapping is virtual like MU then I don’t see any problems, but if domain mapping actually creates a physical URL path then there could be a problem.
Does anyone know?