Godot Engine - Feature-packed 2D and 3D open source game engine.
Clever - syncing between education applications for K-12 schools
MonoGame - MonoGame is an open source implementation of the Microsoft XNA 4 Framework.
PowerSchool - PowerSchool provides a K-12 education technology platform for operations, classroom, student growth, and family engagement.
BYOND - BYOND is the premier community for making and playing online multiplayer games.
Claroline - Claroline is a collaborative eLearning and eWorking platform.