Current documentation is built on top of Sphinx documentation generator. It is released under the terms of the Creative Commons BY-NC-ND 4.0 International License.

You'll just have to install Python Sphinx, it is generally available in distributions repositories for Linux.

If your distribution does not provide it, you could use a virtualenv:

$ virtualenv /path/to/virtualenv/files
$ /path/to/virtualenv/bin/activate
$ pip install sphinx

Once all has been successfully installed, just run the following to build the documentation:

$ make html

Results will be avaiable in the build/html directory :)

Note that it actually uses the default theme, which differs locally and on readthedocs system.