Open Source Software is part of a larger world of ideas. Not all ideas are expressed the way OSS is. The ideas are seen as if they were privately owned.
Copyright began in the US as a limited monopoly of 14 years to encourage authors to create useful and original work. Since then Congress has gradually changed copyright several times. Ideas weren’t originally regarded as property, but now are commonly called “intellectual property” which gives the impression that somebody owns the idea, not just its expression.
The Canadian Broadcasting Company recently produced a radio program about copyright in the modern world. It is worth hearing. You might even want to download the MP3 and use it with your students to explore legal uses of the icons and expressions of modern culture. You might be surprised to find out how long copyright extends beyond its original limit of 14 years.