Query on IITB-Monash JDP

My friend got a offer for IIT Bombay- Monash Joint PhD but is hoping for a better offer from abroad universities and is confused whether to accept iitb offer. So, is there any provision you cant leave once you join the Joint PhD? or any procedure exists to take an exit if? Friend is afraid that they might blacklist or whatso if they reject/ leave later. Anyone here have an idea regarding this?