The Indians explicitly put in the contract that the submarines had to have AIP. And when I say had to have AIP, they meant in actual use somewhere. That basically restricted their choices to only a couple contractors. AFAIK the Germans are the only ones who made a working design with PEM Fuel Cell AIP. The other systems use Stirling engines derived from Swedish ones.
The Indians did have a program to put their own design Phosphoric Acid Fuel Cells on the French derived submarines (Scorpene) they were producing. But that program seems to have gone nowhere thus far.
I personally think the PEM Fuel Cells are a mistake. Those German submarines require dedicated port facilities to refuel the submarine since the thing runs on oxygen and hydrogen. And the submarine can only run at really slow speed while on fuel cell power anyway. It does have one advantage, I guess, the exhaust of the fuel cell is basically water. Good luck detecting that exhaust with the fancy chemical detectors in the latest US anti-submarine airplanes.