Managing the organizational and software complexity of a comprehensive open source digital library system presents a significant challenge. The challenge becomes even more imposing when the interface is available in different languages, for enhancements to the software and changes to the interface must be faithfully reflected in each language version. This paper describes the solution adopted by Greenstone, a multilingual digital library system distributed by UNESCO in a trilingual European version (English, French, Spanish), complete with all documentation, and whose interface is available in many further languages. Greenstone incorporates a language translation facility which allows authorized people to update the interface in specified languages. A standard version control system is used to manage software change, and from this the system automatically determines which language fragments need updating and presents them to the human translator.