One of the major benefits of open source software is the public collaboration behind each project. Most open source projects are created by tens of thousands of programmers all collaborating to create, and improve upon, a flawless website framework.
Many software development companies use a proprietary, or home built, system as the framework for the websites they create. Open source software, such as WordPress and Drupal, were developed by thousands of talented developers. What would you rather own, a software package created by a handful of developers, or a software package created by thousands of developers?
Open source software promotes software reliability and quality by supporting independent peer review and rapid evolution of source code. A proprietary solution can not compare to that of open source.