RE: what's my role in the core team: I try to do whatever needs to get done, that isn't getting done. Today I'm cross-compiling the 0.8 release and testing it on Windows, trying to track down a crash-at-exit issue and an excessive-memory-use issue that seems to only happen on Windows.
When I'm not doing nitty-gritty things like that, I try to work on big, what-is-most-likely-to-make-Bitcoin-succeed problems.
RE: why pay me a salary? "why pay for the cow if you can get the milk for free?"
I told myself (and my wife) a couple of years ago that I wasn't going to sink dollars into Bitcoin-- that I'd sink time into it, and that I'd EARN bitcoins by starting a bitcoin-related startup.
Well, there's enough core development work to keep me busy full time. I wasn't very happy doing core development work AND trying to make ClearCoin happen; I'm happier when I can concentrate on one thing. Besides, having my own startup introduces potential conflicts of interest (ClearCoin sparked conspiracy theories about why I push for multisig transactions so hard).
RE: what if I get hit by a bus?
Then the other core developers will carry on without me. I'm not indispensable.
RE: Why should you join the Foundation? What is in it for you, personally?
That is a hard question, because you can "free ride" -- if we're successful making Bitcoin successful, everybody will benefit. Personally, I don't respect people with that kind of "I'm not going to do it because I'm sure somebody else will" attitude, and I think in the long run the people who take the risks and roll up their sleeves and do the work needed tend to win in the end.
Really, the main benefit of joining the Foundation is it is an organization full of people who are rolling up their sleeves and doing the work. If you're smart, you'll realize that networking with those types of people is to your long-term benefit.