Why develop free software?

One of the things that people ask when they come first across Free Software is 'why would anybody want to develop software and then give it away for free?'There's an editorial in Free Software magazine that tries to explain this conundrum:'The answer, as amazing as it sounds, is 'convenience'.' It makes life easier and simpler for the developer if other people are using the software that they adapted or developed - it saves them more work in the long run keeping it up-to-date and is therefore 'cheaper'.As the comments point out, the article is maybe not a piece ready for the general public but it seems to cover all the points.Anybody know of other resources that cover this point?