Proprietary software (e.g. Windows XP) is own by a company, they own the source code (i.e. basic foundation of a program) and the code is built in isolation by their developers. Whereas the principal of open source software is based on the fact that the source code is freely available online and anyone can use it for their own use (without paying to use). Most importantly often a community of developers contribute to the the development of the software. This model works for the same reason that Wikipedia works; based on the Wisdom of Crowds – increasing the number of individuals working together collaboratively increases exchanging of ideas.
To me Firefox is a classic example of the potential impact open source software. Firefox is an open source web browser which many people are starting to use as an alternative to Internet Explorer. Since it’s release on November, 2004 its usage as a web browser has risen from 4.64 % (Dec, 2004) to 15.10 % (Mar, 2007) compared to Internet Explorer that decreased from 90.31 % (Dec, 2004) to 78.57 % (Mar, 2007) (data from Market Share by Net Applications). I, like many others, use Firefox as my preferred browser because I find it has more functionality compared to Internet Explorer. I originally installed Firefox because Internet Explorer kept crashing when I was using WebCT 6.0, and I do not have any problems with this happening with Firefox. Also Firefox has some great add-ons that make it such an excellent web browser.
Currently the biggest reason why more people do not download open source software is that they do not feel comfortable with the idea of installing software on their computer (in case it damages their computer). Increased user confidence over time will, I believe, lead to increased usage of open source software.