The concept of open source for software development, projects, source code, and the like pertains to the notion that it is available for public use, can be modified and freely shared. It embodies the community-based philosophy where open exchange of ideas and collaborative work is embraced for the sake of perfecting an idea, source code, a project, etc. You must still agree to terms of use just like you do with agreement licensing for proprietary software use but the terms are greatly different. With the open source agreement users are typically granted permission to use the program any way they wish. They just need to be willing to allow others the same accessibility when they share their work. Open source is usually free but there are some instances where the owner of the software or application will charge a fee. However, this is usually reflected in the form of charging for software services and support. Essentially, the software continues to be free but services like installation and troubleshooting have a fee.