I filled out an application like a month ago, I tried e-mailing and calling them and got no responses on either trys. Just the other day I got an e-mail back saying my application was rejected so idk, i don't they are currently letting anyone in...
A few months ago they were going through some money troubles and ended up cutting thousands and thousands of affiliates from the network, keeping only the highest performers (me included :-D :-P). This is probably why they're not accepting many now, too.
Hydra definitely tightened their affiliate acceptance policy. Unless you're a big fish, I wouldn't try right now.
I tried like a month before, received a call from them and was told that i'll hear from them in couple of weeks, but nothing yet.