You don’t have to pay society maintenance 

builder can deliver possession of flat only after obtaining OC 

builder cannot deliver possession until OC is obtained 

society has to recover maintenance from the builder 

At the outset, since you have not taken possession of the flat and the builder has not obtained Occupation Certificate (OC), your legal obligation to pay society maintenance is not automatic.

Maintenance liability generally arises when:
you take possession, or
you start enjoying/utilizing the premises.

In your case, neither has happened. Therefore, prima facie you are not liable to pay regular society maintenance.

Further, a society formed by occupants who have taken possession without OC does not automatically bind non-occupying purchasers like you, especially when:
you are not in possession,
you are not using common facilities, and
the builder has not completed legal formalities.

However, there are a few practical nuances you must be aware of:

Firstly, some courts have held that even non-occupying flat purchasers may be liable to pay proportionate charges for basic maintenance of the building, particularly if the society is incurring expenses for common services (security, electricity, lifts, etc.). But this is usually limited and not equivalent to full maintenance.

Secondly, your primary liability is actually against the builder, not the society. The builder is responsible for:
completing construction,
obtaining OC, and
handing over lawful possession.

Thirdly, the society’s threat of legal action is often a pressure tactic, but if they do file a claim, you have a strong defence based on:
no possession,
no OC, and
no usage.

Your best course of action would be:

Send a written reply to the society clearly stating that you have not taken possession and therefore deny liability for maintenance.
Keep all documentation showing that possession has not been handed over.
Consider initiating action against the builder (RERA/consumer forum) for delay and non-obtaining of OC.

In conclusion, you are not strictly liable for full society maintenance at this stage, but a limited liability may arise depending on facts. The stronger legal position lies in asserting your rights against the builder rather than yielding to society pressure.

If the flat was not delivered possession then there is no question of paying maintenance to the society.

If they threaten, you send a legal notice through your advocate stating that the demand made is illegal  for the reasons that neither the developer obtained OC nor he had delivered possession of the flat, besides the flat is still under construction or incomplete, hence any demand made towards maintenance should be made to the builder until he fulfills the legal requirements fully and properly. 

Is the society a legally registered body with bylaws? What do the bylaws say about maintenance charges- payment commences when, penalty for arrears etc.? If the society is not duly formed and registered, it has no legal right to enforce any bylaw. Please engage a competent lawyer and ask him/her to send a suitable reply to their demand notice.