To get multiple instances of ReplicatorG on OSX you'll first need to use the terminal. In terminal we can make use of the —new (-n) flag. This will force an additional instance to be opened regardless of how many are already running.
For example it looks like this:
A-MacBook-Pro:~ JudyOMalley$ open -n /Applications/replicatorg-0009/ReplicatorG.app
So far I haven't had any issues.