good to hear that they're on their way back. as for legal options, as i mentioned, you have very few if any choices which are realistic.

in india the denied boarding rules, etc are very murky and as an economy class pax it will be difficult to pressure them into an amicable settlement. also, since you bought the tix from an agent they will blame the agent and you will have to take it up with the agent (who of course will blame the airline and so on).

so i would recommend to try and approach OS in New York and ask them to investigate and possibly give compensation. fighting it out in india will not be easy or cheap.

good luck however you proceed.