i don't think that it is accurate anymore to think of the development process for the linux kernel as "hobbyist".

it is probably a better description of the application space, but even there, it doesn't apply across the board.

people who don't develop software (and even some who do) sometimes imagine that the process inside a company than actually pays its developers is radically different from the one that involves hobbyists. the differences are not as dramatic as you might think, and in the case of particularly small companies, there can effectively be no difference at all.