If it is going to be stored/displayed/used in a commercial(ish) space their insurance should cover it - but everybody has to agree to that upfront possibly including their agent. That should help with the damage/theft fears. Also, how are they going to vent it? If your friend stores it in his home it may or may not be covered (especially if he rents and doesn’t have renters insurance.)
The glowforge is clearly yours and it can’t be used without access to your account, or you having glowforge transfer your account (I believe.) That said, what is legal and what happens are often only loosely correlated. I feel for you, but have no practical solution here.