Money isn't just for working full time. Sometimes you need hardware or software for compatibility testing. For example, suppose you were trying to build parse

Money isn't just for working full time. Sometimes you need hardware or software for compatibility testing. For example, suppose you were trying to build parsers/writers for PSD or XLS files. To test on older versions of photoshop or excel, you need access to those older versions (and most likely, the contemporaneous hardware). Those are real costs. I also think the point regarding focus is misguided: if the money is specifically for embellishments (e.g. 100% compatibility), then you are in fact more likely to embellish Finally, Ruby on Rails happens to be an exceptional example in terms of traction. Most open source projects never come close because the addressable market is smaller (the set of all people supporting a particular ruby gem is a subset of the people interested in ruby) and in those cases a bit of extra money is enough to take a hobbyist effort to a production-level product. That extra work takes time and money (for example, sitting there and validating certain results by hand) and oftentimes won't happen with an open source project.