Fossil has the ability to import and export repositories from and to [http://git-scm.com/ | Git]. And since most other version control systems will also import/export from Git, that means that you can import/export a Fossil repository to most version control systems using Git as an intermediary.

Git → Fossil

To import a Git repository into Fossil, run commands like this: 
cd git-repo
git fast-export --all | fossil import --git new-repo.fossil
In other words, simply pipe the output of the "git fast-export" command into the "fossil import --git" command. The 3rd argument to the "fossil import" command is the name of a new Fossil repository that is created to hold the Git content. The --git option is not actually required. The git-fast-export file format is currently the only VCS interchange format that Fossil understands. But future versions of Fossil might be enhanced to understand other VCS interchange formats, and so for compatibility, use of the --git option is recommended.

Fossil → Git

To convert a Fossil repository into a Git repository, run commands like this: 
git init new-repo
cd new-repo
fossil export --git ../repo.fossil | git fast-import
In other words, create a new Git repository, then pipe the output from the "fossil export --git" command into the "git fast-import" command. Note that the "fossil export --git" command only exports the versioned files. Tickets and wiki and events are not exported, since Git does not understand those concepts. As with the "import" command, the --git option is not required since the git-fast-export file format is currently the only VCS interchange format that Fossil will generate. However, future versions of Fossil might add the ability to generate other VCS interchange formats, and so for compatibility, the use of the --git option recommented.