Jeremi is groupware software for realtime document sharing. It supports distributed work on different documents or files by different people or project groups. It offers an always-up-to-date view of the project and its files and coordinates the dependency of the actual file status and access to those files. Jeremi is written entirely in Java.
Xfiles is an interactive utility for comparing and merging one file tree with another over a network. It supports freeform work on several machines (no need to keep track of what files are changed on which machine). Xfiles can also be used as a cross-validating disk<->disk backup strategy.