It's not a female-only board; it's a female-oriented topics board for anyone. It was originally conceived as a BL/yaoi board (the manliest of all fetishes), but that stuff hasn't been posted much thus far

>Is this some kind of weird feminist website?
Heyuri is more of a weird "the internet was better before netizens turned extremely retarded with feminism and anti-feminism" website. You are free to be a lecherous chauvinist, a self-flagellating lady worshipper, a frigid bore, or a cock-hungry slut on heyuri.net - so long as you don't take it too seriously

Now if all the cock-hungry sluts could just line up outside my office...