PlantUML is an open-source tool allowing users to create UML diagrams from a plain text language. Developed by Arnaud Roques
License: Open Source
UMLet is a user-friendly graphical tool for creating UML diagrams with a focus on simplicity and ease of use, while PlantUML offers a text-based approach that allows for more flexibility and automation in diagram generation. PlantUML is better suited for those comfortable with coding and looking for integration capabilities, whereas UMLet is ideal for users who prefer a visual interface.