For practical purposes, broker bonuses are not legally available to Indian residents. The only forex trading a resident can legally do is in INR currency derivatives, USD/INR, EUR/INR, GBP/INR and JPY/INR, traded as standardised futures and options on recognised exchanges like the NSE, BSE and Metropolitan Stock Exchange through a SEBI-registered intermediary. These are regulated brokerage accounts, not the bonus-driven offshore accounts you see advertised online.
Trading forex or CFDs with an offshore online broker is a different matter. Sending money to an overseas broker to trade non-INR pairs is treated as a FEMA violation, and the RBI keeps an Alert List of platforms, now running to around one hundred names, that are not authorised to deal in forex for Indian residents. Several well-known international brands appear on it. Because these brokers cannot legally take your funds, the bonuses they attach are not offers you can safely act on.
If you see a deposit match, cashback or no-deposit credit aimed at Indian traders, assume it comes from an offshore broker operating outside FEMA. Penalties under FEMA can reach three times the amount involved, and getting funds back from an unauthorised platform is difficult. A bonus is worth nothing if the underlying account is not one you are permitted to hold.