OpenMoji

OpenMoji is an open-source emoji set from the HfG Schwäbisch Gmünd (a German design school), created by Benedikt Groß, Daniel Utz and more than 70 students and outside contributors. Its style is a flat, outlined "sticker" look with a consistent stroke weight.

Pick Emoji bundles OpenMoji and serves it from this origin. Every emoji page carries an “Across artwork sets” section putting this set beside the other four for that emoji, so the place to see what OpenMoji does with any given character is the character's own page. The repository linked below is the set itself, and Licenses carries the attribution every one of these sets requires.