What Is Open Source Programming?
At the simplest level, open source programming is merely writing code that other people can freely use and modify. But you've heard the old chestnut about playing Go, right? "So simple it only takes a minute to learn the rules, but so complex it requires a lifetime to master." Writing open source code is a pretty similar experience. It's easy to chuck a few lines of code up on GitHub, Bitbucket, SourceForge, or your own blog or site. But doing it right requires some personal investment, effort, and forethought.
Let's be clear up front about something: Just being on GitHub in a public repo does not make your code open source. Copyright in nearly all countries attaches automatically when a work is fixed in a medium, without need for any action by the author. For any code that has not been licensed by the author, it is only the author who can exercise the rights associated with copyright ownership. Unlicensed code—no matter how publicly accessible—is a ticking time bomb for anyone who is unwise enough to use it.
Read more at OpenSource.com