It translates to "free of charge" or something to that end.
Ubuntu is a Bantu (broad language family of about 600 African languages including Zulu) term meaning something like "humanity" or "community"
Near as I can tell, Granel is borrowed from spanish and in isolation would mean "grain"
"A granel" in Spanish means "in bulk". It's used when you go to a store and you put however much of whatever you need in a bag. Usually done with veggies.
"Ubuntu a granel" means "Free of charge" in Kinyarwanda (according to Google Translate).
Edit to add: It's spoken in Rwanda.
