The problem is that one transaction is linked to one user (on license), and a gblink will have the transaction id (orderid) inside of it. I remember we were playing with a 'free' transaction type before I left, but I'm not if that got into 4.1 or not.
The easier solution is to not send a gblink URL to the users, but to send a link to a service on your server that responds with HTTP 302 (or 303) redirect to gblink URL that the service computes with a brand new transaction id.