A little déjà vu that I posted in a recent thread:
http://www.merriam-webster.com/dictionary/nerd
http://dictionary.reference.com/browse/nerd
http://en.wikipedia.org/wiki/Nerd
And now for my two pennies.
Based solely on the definitions that I've linked to, I'd lean on the "negative" side. While we could go on a mission to redefine a word that has been around longer than FIRST itself, I think we're better off pushing that term to the back of our mind when it comes to describing the [widely-varied] participants in the program as a whole.
FIRST, while being a very tech-minded program, attracts all sorts of people. Some of them go on to be business entrepreneurs, others graphics designers, and, of course, engineers, programmers, and everything in between. So to assume that the star basketball player or the girl who is the leading role of the school play are nerds, is wrong. At Buckeye (the only regional I've ever attended), I see all sorts of people, some who would (rightly) be offended by being called a nerd. They listen to all sorts of music, they're from various parts of the city, some of them are really outward people. But because they're a part of an activity that involves a bit of science, they should automatically be labeled a 'nerd'?
And to be honest, even those of us who ARE techies or engies and are a part of FIRST aren't "nerds" in the true sense of the word. For one, if we're so darn socially awkward, why are we interacting with a group of people for 6+ weeks, then going to a large event akin to a sports game and mingling with hundreds or thousands of others? And as I mentioned earlier, some people are a part of their school's athletic programs, so they must be at least somewhat physically fit.
I know my long posts are generally full of flawed logic and rambling, my point is, unless you can convince the dictionary (and our entire society) to redefine the word, it's best not to apply it to an entire organization that represents a huge range of personalities, some who are anything but nerds.