I wasn’t aware of the restriction on foreign carriers but why haven’t any other Indian carriers, besides GoAir, launched international operations from Kannur despite the airport having opened for commercial flights for over a year?
Kannur's attraction as an airport , for the airlines, is more so for int'l services to the Gulf just like it's similar neighbour Calicut (CCJ). But bilateral seats are exhausted to most prominent gulf markets like Dubai/Doha etc.
Their domestic market, is some what similar to Calicut too again, having sporadic demand to select few cities only. Hence, India's largest airline, IndiGo, serves Kannur only with ATR's for domestic services. And only one sole int'l service now to DOH on airbus, after pulling out of KWI last month.
GoAir just cancelled their second daily day service to BOM, and operates only a red eye flight now. They have regular service to BLR and weekly services to HYD/MAA.
So opening Kannur as a station now by other Indian airlines just for domestic services is definitely not worth it.
Regarding Int'l airlines at Kannur, even Mangalore being such an old airport hasn't yet been made a point of call for int'l carriers despite being popular for gulf connections since decades. So not sure why Kannur thinks they'll get that privilege just right after opening their new airport.