Open source release: https://github.com/q2apro/q2apro-booker - but it's a release with no support. I did not even test it on a fresh installation. Any support can be done by the community.
Btw, included is a complete cool theme, see qa-theme folder.
And check the code, it is full of features:
- integration of payment systems,
- booking calendars, ICS, Google Calendar integration,
- premium membership,
- rating system,
- classifieds (offers and requests),
- and more. See also here and here.
DEMO: https://en.kvanto.lt/ (guess I will sell this site soon, so no guarantee if it will still work.)