Simply put, the open-source movement has proven beyond a shadow of a doubt that you can develop great software with dozens of developers using collaborative work techniques. Certainly, much of open source's success lies in its underlying philosophy. For more on that, we point you to the online seminal works of Eric S. Raymond . The mechanics behind open source can be useful, even if you'd rather die than publish software under the Free Software Foundation's GNU Public License. Open source's methodology pointed out a different way.
Most people think that hundreds of developers work on the typical open-source program.
Sure, thousands of people fiddle with open source. But it usually takes no more than 20 developers to do the vast bulk of the actual development work. Additional programmers usually contribute a few lines of code and are invaluable for quality assurance and bug finding. There are key differences between open-source projects and proprietary development methods. Many, if not most, proprietary projects rely on nontechnical managers to run software development.