Firebird

URL: https://firebirdsql.org
licence: Interbase Public License, Initial Developer Public License
platforms: Unix, Win 32/x64, Mac OS X

Pros

Powerful and stable cross-platform database
Extensive SQL standards support
Python driver binary distribution available for : Mageia ,Fedora, Redhat , FreeBSD (Debian, Ubuntu will come soon) but you can to compile and install easily for other platforms : here is the Howto install it on Ubuntu with pip.

DB API 2.0 Drivers

Python 2.x-3.x Driver (Official Stable)

Pure python ctypes based driver (fbclient library is required) is located in svn repository (All official driver development is done in this repository) In addition to feature set of the standard Python DB API, fdb also exposes nearly the entire native client API of the database engine, including two-phase commit, server-side events, and an administrative API.

URL: https://firebirdsql.org/en/python-driver/
GIT: https://github.com/FirebirdSQL/fdb
pypi: https://pypi.python.org/pypi/fdb/
Documentation: https://pythonhosted.org/fdb/
Python versions: 2.7 - 3.x

It was tested with cpython

Pure Python 3.x Driver

New pure python 3.x driver (no C compiler needed or fbclient library) development is located on github repository

URL: https://github.com/nakagami/pyfirebirdsql
pypi: https://pypi.python.org/pypi/firebirdsql/
Documentation: https://nakagami.github.com/pyfirebirdsql/
Python versions: 3.x

It was tested with cpython , jython, ironpython and pypy