More specifically, it is a certification standard issued by the Open Source Initiative (OSI). In order for a software license to meet this standard, it must:

• Free Redistribution
• The distributed program must make the source code accessible to the user
• The author must allow modifications and derivations of the work under the program's original license
• No person, group or field of endeavor can be denied access to the program
• The rights attached to the program must not depend on the program's being part of a particular software distribution
• The licensed software cannot place restrictions on other software that is distributed with it.