Open Source and other 85,000 icons from Icons8 icon pack follow the visual guidelines of the operating systems: Windows, iOS, Android KitKat, and Material. PNG format is free up to 100x100 px. Icons are availble for download in PNG and vector (SVG, PDF, EPS, and more).
The icon is basically identical to the logo used by the Open Source Software community. The Open Source Software community is a collection of developers who work toward the creation of software and tools whose source code is released with a permissive license, for all to use and modify with few restrictions.