The Open Source Initiative (OSI) is a non-profit organization that promotes the open source idea, specifically in connection with the certification program.
The certification program certifies the open source programs that meet all the requirements regarding an open source. This gives the user security in terms of unrestricted access to all information concerning the source code. He can further develop and distribute the software.
The idea behind this is relatively simple: If the programmers have insight into the source code, are allowed to modify it and distribute it, this software will continue to develop with constant improvement. The developers improve and adapt it and will remove bugs.