I replaced my return rebTripwire(); 's with the return Init_Tripwire 's
Alas, this did not resolve the segfault when closing the window.
I take it that both methods to return a void are actual and functional.
So....
It appears I resolved the segfault issue now!
Of course it was my own stupid mistake(*), not connecting the right information in the signal-connect function.
I can now exit the window and return to a working console again.
Next step up is get a Rebol function to act as a valid callback function. (**)
(*) The stupid mistake only to be taking up this work 
(**) Check for the latest update on this the ever growing GTK3 GUI thread ( Just moving ahead now with GTK3 - #18 by iArnold )