What is the loot?
Makemytrip has introduced a feature known as 3x Refund for tickets that get cancelled due to train ticket remaining in waitlist.
As you know in india , there are many such busy routes where getting a confirmed ticket is very difficult so if you find few such you get free refund/bonus.

How to Avail?
Search for patterns/routes which have very low chances of confirmation , you can use rail predictions apps and other analysis.

Book the route with MMT 3x Refund Guarantee and Get 3X Refund on train ticket not getting confirmed.

https://www.makemytrip.com/promos/trains-trip-g...

Is it Free?
No there is a risk/investment involved for the amount ticket is being purchased,but if utilized in an efficient way would benefit everyone.

Is it Ethical/Legal?
Ideally this promotion is introduced by mmt to benefit genuine train travellers who might face cancellation on lastday and still want to travel could use this to get additional refund which they could actually use it for travel.
But as i have observed , people are silently exploiting this promotion/offer and henceforth trading such 2X refund coupons for cash.