Klaus,
Unfortunately, localization is not on our near-term project plan, but certainly is something we would like to support. HTML hyperlinking is bubbling to the top or our priority list, but we don't have a date that we're ready to publicly state yet.
You can have 5 users working on the same project by storing your project files on a shared server and accessing using a UNC path (e.g. \\servername\projectFolder\Myproject.ucd). You will need to break your use case model into packages (the UML term for folders) and store each package to a separate file (right click on the package in the model browser and select "save as separate file"). When CaseComplete opens the main model file, it automatically loads the package files, so to the user, it appears as if you working on just 1 model file. Each person can have the model open simultaneously but you have to make sure two people don't modify the same package file (or glossary) at the same time. You should set up clear responsibilities of who can modify which files, or set up a communication system in which you can easily see who is working on which package file.
Hope this helps.
Doug
Serlio Software