OpenLP is open source church worship presentation software. Basically, we make the words appear on your projector screen so that you can sing in church. But we also do Bible verses, presentations (PowerPoint, LibreOffice), and custom slides. We even have a remote control!
OpenLP is a mature application, with a team which has been around for more than 10 years. It is also truly cross-platform, and runs on Windows, Mac OS X, Linux (Ubuntu, Fedora, Arch, openSUSE, etc) and FreeBSD.
Like all open source projects, however, we have certain costs. Most of these costs have been borne by the developers up until now. With Gratipay, we are giving you an opportunity to give back to the project monetarily, in a way that will help us with our monthly costs.