The entry point for bio4j documentation is at the main bio4j repository. All content of wiki that was here has moved there.
In general, bio4j documentation is written in markdown, and it is kept together with the corresponding sources, inside the repository docs folder. This way docs are automatically in-sync with versions, and we can easily maintain documentation for different versions.
If you feel that something is incomplete, can be improved or is just wrong, just open an issue or send a pull request!