The law is not yet settled on this issue and the matter is pending before the Supreme Court and Delhi High Court. The argument used by these websites is that poker is a game of skill and hence should be exempted from the provisions of the respective state Gambling Acts, and under that presumption they have started the website. This is a very convincing argument but is yet to be accepted by Courts of law in India (especially as far as poker is concerned).
So right now, I would say that the position of law is uncertain; but once this is settled no specific permissions would be required; however Income Tax has to be deducted before awarding winnings over Rs. 10,000/- and needless to say compliance with all regulations and laws for the time being in force in India would be mandatory before proceeding with anything.
For more information and updates please visit my website http://www.glaws.in the first and only website on gambling laws in India.
Regards,
Jay.