Gentleware AG | 40 followers on LinkedIn. Gentleware AG was founded in 2000 in Hamburg, Germany with a strong basis in the the open source project ArgoUML. In addition to the product line "Poseidon for UML", the firm also offers training and consulting as well as tool customization for high productivity software engineering. "Poseidon for UML" is the world's most downloaded commercial UML tool, with over 1,200,000 copies distributed to over 100 countries.