Open source can be defined as: The practice of development, in may cases, of computer software where the source files or codes are made freely available to the public. Open Source presents a framework that in many cases have been tried and tested. Hundreds or sometimes thousands of programmers work to create one solution.
Examples of popular and widely supported Open Sources for Internet businesses include; Joomla and Drupal for web development, OS commerce, Magento, zen cart etc for shopping carts
When your system is built through Open Source, you have thousands and sometimes millions of other users using a similar product, if you run into problems, all you need to do is post a question and within hours and sometimes even minutes, someone with a similar problem or who has encountered a similar problem before will be able to provide a solution for you
Using Open Source presents you with wide choices. Because there are many developers who have access to the codes, you can easily get another developer to customize your project should the first one fail. When your system is developed from scratch, you are at the mercy of that particular developer, if you were to transfer that code to a second programmer, not only will the second programmer have a steep learning curve, if the system was not built and documented in accordance with a standard methodology/development procedure, then the second programmer might find it absolutely impossible to build upon it
Contrary to many claims that open source are not secure, open source are secure and this is why; when you use an open source, thousand other developers take time to test the code. If vulnerability is discovered, a post is made in the discussion forum or an email is sent to subscribers
Using open source involve sharing, if one person encounters difficulty e.g. if their website is hacked, they will be able to share it in the forum and thousand other people will instantly become aware and take the necessary steps
Regardless of good your programmers are, there are less chances they would compete with complexity of some of the open source available especially on a shoe string budget. The reason being, some of the open sources have been developed over years and the teams of experts keep revising it and developing it. It is no surprise to find an open source which is up to 10 years old.