I started to using the useful Intro.js library in my project, but after few months use I updated it and found that the license changed on 08/03/2016.
The library is definitely open source and free software, but at the same time if I want use it for commercial use it seems I need to pay a license fee. Why is this required if the code is open source?
Maybe I'm missing something because I'm new in the license use world.