They still need permission from said specific country.Why would India need permission from all these nations to sell Tejas to others? I understand your point about the American engine in Tejas, but how does having a mix of foreign weapons alongside Indian ones in Tejas pose a disadvantage?
A country buying Tejas has the freedom to select any weapons they prefer for Tejas, whether they are Indian, European, Israeli, Russian, Japanese, Korean, or from any other country.
Say if they go with Russian weapons, gotta need permission from Russia (and so on with the rest as well).