Furthermore, since there's no requirement to keep the source code secret, a much larger of number of programmers can work on any given project, and they don't have to work for the same company, or even live in the same country. However, the lack of this resource horizon does not mean that Open Source software has no limits, it just means that the limits aren't financial.
Commercial companies make software for money, so money is the limiting factor.
Open Source developers make software for the love of the thing, so love becomes the limiting factor as well. Unloved software can't be built using Open Source methods. Open Source software trades the resource horizon for an interest horizon, the horizon over which a problem simply isn't interesting enough to attract a group of developers who burn to spend their Friday nights wrestling with, say, meter-reading software for a natural gas pipeline. This is geek nirvana, where interest and innovation have more weight than profit or productivity. Wherever Open Source is a good way of working, it is more effective than closed source, for the same reason that open markets are more effective than central planning.