What was that. I felt enlightened, finally. I've made several researches about licensing and copyrights. However all of them end up being reading all the licence files and give up at some point. Seen several articles which were trying to keep it short also teach me nothing. At least now I have a better understanding about how it goes, about permissive and protective distinction. 
However I'd like to see another more in depth information about graphical content since it's more of my area and as I know yours as well. 
You explained what should be done from project's perspective but I still don't know how should I approach as a graphic designer to an open source project. Let's say when I design a logo for a project I just share it with cc license and that's all, I don't even adding font licenses since I think they are already known as open sourced (thanks to google fonts.) I don't know what should I do to make things more clearer or at least look more professional.