It's not necessary to be a native English speaker in order to publish in Hubpages. That said, the quality of one's grammar, spelling and punctuation will affect the ratings of one's hubs to some extent.
However I'm mostly interested in content. And if I can understand what's being said, I'm not picky about linguistic gaffes on the part of writers, for whom English is a second language.
Putting things into perspective, I don't even have a second language!