Open source is a term used to describe a certain type of development method. Open source development means that everything related to the code that makes up the software is free for people to inspect and see.
This is very different to the typical development method you would see in most software which is closed source. In closed source development the original code that was written for the software is not accessible by the public.
The program is complied before it is distributed and as such the inner workings of the program are not accessible.
This method of software development is very common in commercial software because it prevents a developers competitor from viewing the source of a program and copying it.
What does open source mean for development itself?
One of the big advantages of open source software development is that its much easier for an entire community to get involved in the development of software meaning that required changes (such as important security updates or new feature additions) can be identified, coded and implemented much faster than software developed under closed source practices. This is made possible by the nature of open source software and the fact that anyone can access and work with the current source code.
What does open source mean for longevity of software?
One of the most important examples of open source software is GNU/Linux. Linux was developed by Linus Torvalds in 1991. It was based on a current derivative of a Unix system at the time.
Linus had a fantastic grasp on software development at the time, but felt restricted by the fact that Unix was not open source. Linus was more capable of further developing the software than its owners, so in order to get around the issue of the closed source development practices he re-wrote the entire kernel from scratch and registered it under the open source licensing agreement.
Linus went to these efforts because he strongly believed that the software should be open source and that it was needed to ensure the software was developed in the best way possible.
Getting involved in open source projects
Whether you are an experienced software developer or you just have a keen interest in the field, open source projects are always very exciting to be involved with.