There are plenty of ways to stop this infact i just had another idea ( so the person poaching doesn’t claim the signup)
allow the person to be free if he wants to use your program , plus another program thats fine ( but don’t give the poacher the credit)
You could do it the opposite way – get the player to tell you what program he is getting entised to create an (affiliate oposition refer back link ) that if they want to go to that program aswell thats fine ( get them to state the program they have been enticed to ( you the program create a link hardlink to the opposition that you are getting entised to. not the poachers link.)
and you let them go if they really want to but if they want to come back that hard link you provided to go back to they
claim the bonus back.