Does "brogrammer" mean male programmer? No.
(The 26th result is from a woman's profile on Facebook who commented on a link about brogramming.)
My brother and cousins are increasingly "brotastic", with tough talk, and repeated high fives (followed by finger pistols). And they didn't even get it from the aforementioned chans; it grows naturally. As scary as that may be to the rest of us.
So, if the term sexist? That's two questions:
1. Is it intended to offend or drive away women? Probably not.
2. Is it offensive to women despite intent? Not for me to answer, as a man. But this is the more important question.
(Sorry, lots of editing. I realized I had a lot more to say. But if they wanted to go for this style, they could've just as easily made the first line say something like "looking for awesome dudes and lady-dudes with awesome skills and awesome personalities to join our awesome startup!" Or something as cheesy to ensure inclusion.)
1) Yes, even if implicitly. It says "I expect people to conform to masculine norms; everyone else need not apply." Whether or not they specifically set out to exclude women, they did set out to exclude everyone who wasn't willing to tolerate their sexist and exclusionary behavior, who will statistically be more female than male (though plenty of men are excluded too.)
2) Yes it is. Plus, as men stated up stream, it is directly offensive to some men too, and it should be offensive to anyone who doesn't want to work in a field populated by sexist assholes.
I certainly don't think women would want to be called "programmerettes" or "programmeresses" en masse. And I'm too afraid to Google those.
As to the points I was trying to make, my intent was to say that yes, I believe it absolutely would drive off more women than men by appealing to a culture that is male-dominant. But I wouldn't go so far as to suggest that it was done with the explicit intent of establishing a "no girls allowed" company. I do think those guys should've been more thoughtful about who they were appealing to, and I'm glad MattManser brought it to our attention; it's an interesting read. But I'm not as quick to call them sexist assholes. For all I know, they were going for a sense of cultural fraternity (that someone earlier in the thread excellently brought up as a word that, despite its roots, is a feeling we all typically aim to share.) Then again, that leads directly to my second point...
Being a part of that culture? That isn't a place I would want to work, either. But just because I find something untoward doesn't mean everyone would. That's what I mean when I said women get to decide what's offensive toward them, not men.
If men think something is offensive toward women, and women don't... Then I think it would be a very odd argument indeed. I think men can have an opinion on it, and I think most of us here probably agree it's at the very least tasteless, but matter like this, I would tend to defer to the party claiming offense. The question becomes what makes HER feel uncomfortable, and avoiding that.
It's something polite that could be done with anyone on any topic, but especially should be if the vast majority of a group finds it shockingly offensive.