Jeez guys, this isn't that hard.

Genderlock simply means "you can't do X thing in our video game unless you play as Y gender"
In this case, X thing is "play Viera race"

For some reason, some people seem to think this is something that only applies to playing certain character classes, even though the term "genderlock" doesn't necessarily allude to that at all and there is more to what certain players might want to play as aside from character classes