Open source refers to an *openly distributed* program code (including codes that are *free of charge*) that can be *utilized* and *modified* by the end user *without restriction.*
[TIP]
----
====
There is now solid metrics data from Google's https://googleprojectzero.blogspot.com/p/about-project-zero.html[Project Zero^], Google's security research team, that https://googleprojectzero.blogspot.com/2022/02/a-walk-through-project-zero-metrics.html[Linux developers are doing a faster job of fixing security bugs than anyone else^], including Google.
The researchers found that open source developers *fixed problems on Linux in just 25 days* on average. In addition, Linux developers have improved their speed in repairing security vulnerabilities from 32 days in 2019 to *just 15 in 2021.*