an Open Source BPMN 2.0 / DMN 1.1 Modeler
Syntax tree editor for rapid annotation of existing text
PUed - PlantUML Editor
A free cross-platform editor for the DRAKON visual language.
The markup language for design the programs
A PlantUML editor written in Qt4
OpenGL 3D Mesh generating library
Simple petri net editor
Web-Based UML Diagram Tool