Why should I pay for a commercial Edition when PostBooks® is available for free, and there's an open source community working on it? Won't the child surpass the parent at some point?

Part of what a vendor has to be comfortable with in the open source software world, especially if they're pursuing a dual-licensing model such as xTuple, is competition between the free and commercial versions. Fundamentally, we believe it will come down to how well we do our jobs managing the PostBooks® community. If we're unresponsive, don't give a good sense of overall roadmap and guidance, or needlessly antagonize community members, there's a good chance the project will be "forked" — and maybe someone will start a PostPostBooks project. But our hunch is that there's a much bigger interest in expanding PostBooks® horizontally — into adjacent markets and with modular add-ons — than in trying to duplicate the tested and battle-hardened functionality in the commercial Editions.