Right, the message comes up when the oRBs_registerPref function is called.. which shouldn't be called unless oRBs is installed, assuming the add-on author used the correct way of hooking in to RTB/oRBs. It appears many don't and simply check for the existence of the function instead, which is something we didn't anticipate.
Per RTB/oRBs documentation, developers should check for a global variable when registering prefs. If it's not set, load RTB. If RTB doesn't exist, then don't call the methods. With Glass's compatibility, the oRBs global variable is not set, leading us to assume correctly implemented add-ons wouldn't still try to register oRBs prefs without oRBs.
What you're all asking for is also what we implemented (or at least intended to implement), but with evidently incorrect assumptions about authors' implementation of RTB prefs. We'll work around broken add-ons in the future, I suppose.