You could have downloaded XMasLights 1.5.8 for Mac from our application library for free. The program belongs to System Tools. This free Mac application was originally produced by Jeff Sauer.
From the developer:
This little, yet powerful application will provide you with a simple strand of holiday lights for your desktop. You can easily download this widget for free from the developer's web site and decorate your desktop with the wonderful animation.
For more strands, simply run multiple instances of the Widget.
You may want to check out more software for Mac, such as Unite Media Player, Stay Secure or Wikipedia, which might be related to XMasLights.