Yes, there are many brokers who have set up offices in India. You mentioned Alpari. I called Alpari India to learn that they offer trading only in 4 INR pairs on NSE and MCX. It doesn't even involve the MT4 platform. So, Alpari is providing nothing different than any other broker in India like icicidirect or sharekhan.
There are some other brokers who have offices in India, e.g. FXCentral. Although they say it is FXCentral India, the firm is registered as "FxCentric India Ltd", a group company of Fxcentral. It is registered of offer Financial services but not "Forex Trading" in particular.
Here is the RBI Circular on RBI site itself:
https://www.rbi.org.in/scripttts/BS_CircularIndexDisplay.aspx?Id=6336
I don't know the legalities of trading spot forex in/from India, may be there is no such law 'against' it but just warnings but I have stopped trading forex for now. I am hopeful that since many brokers are opening offices in India and specially Alpari who is actively involved in promoting Forex Trading (at least on NSE, MCX derivatives for now) they may allow trading in coming years.
There are people trading forex actively with many brokers. They may also be making some money but I have decided to stop. The markets are here to stay. I can wait too. Apart from this, its individual's call to trade forex or not.
Thanks!
Nikhil