Are you inferring that only users of BitcoinTalk will be able to take advantage of the airdrop? To be fair, yes, this is a trick question, but a legit one nonetheless.
No, the airdrop is not exclusive to Bitcointalk accounts. They are valid forms of online presence if they are not obvious throwaway accounts and have some history of legitimate engagement. Any online presence is valid - there is no discrimination on the basis of platforms.
All members of this forum?
Edited because this question was missed in reference to the comment on Decred's international community. What this means is the project is seeing global participation. At present, participants have come from over 100 different countries.