If they're really looking to use the money to expand into Enterprise territory, I think it's a really different game.
I think the bootstrapped B2C game is ALL about saving money/not going broke. It's most accurately about making great decisions (it always is, at any level), but I think for what they were doing, that meant not spending. Their management/founders might have been great at that. I think it's very much an engineer's mentality, anyway.
However, B2B is a different animal, I think, and one that Tom Preston-Werner might not be geared to hunt -- at least not until someone turned him on to how much bigger GitHub could be. It's not cheap to get the attention of big companies, neither in pursuing them at all, nor in buying the people you need to pursue them -- engineers usually can't do this by themselves. You need veterans of _that_ game and it's a different game (at least from what I've seen).