Open source software is computer software that is available in source code form. The source code is provided under a software license which permits the users to use, study, change, improve, and distribute the software. An example of the source code is as seen for the
mean function in Section 1.1.
Open source software is made available for anyone to use or modify, as its source code is made available. The software use is subject only on the stipulation that any enhancements or changes are freely available to the public. With open source software, users, scientists, engineers, and everyone else, are granted the right to both of the program's functionality and methodology. The users only have the rights to functionality of a proprietary software program.
Definition from the Open Source Initiative (OSI) Foundation Introduction
Open source does not just mean access to the source code. The distribution terms of open source software must comply with the following criteria: