Download, open the DMG, then double click to install (requires OSX 10.6 or better). It should select itself as your current screensaver, and also put an icon for the application on the desktop. If not, open the System Preferences / Desktop & Screensaver and choose "Electric Sheep" from the list on the left.
Release notes for 2.7b36:
- removed support for OSX 10.4, 10.5, PowerPC and 32-bit (!). ES now needs at least OSX 10.6 on 64-bit processor. The legacy platforms were slowing down the progress and making the code maintainability harder and harder.
- improved full screen behaviour of the standalone application.
- the binaries are now signed with required signature method for OSX 10.9.5 and up. No more security warnings.
- sealed all remaining resistant memory leaks I could find.
Many thanks to Daniel Svoboda for maintaining this client!
If you have trouble, see the help page.