SimpleGal is distributed via the honour system. Its suggested value is $15 USD; if you can’t afford to pay, or just don’t feel like it, then you can still download and use SimpleGal freely. However, developing and distributing SimpleGal costs time and money, and payment—no matter how little—is very much appreciated.
You can pay via the donate page.
Latest stable version
The latest version of SimpleGal is 3.2.
If you have a version of PHP less than 5.0, you can only run versions of SimpleGal up to and including 3.1. Old versions can be downloaded here.
Development releases
You can download the latest development releases by using SVN; the latest development goes on in the trunk of SimpleGal’s SVN repository:
http://svn.simplegal.com/trunk
The usual warnings apply: development releases are inherently unstable, so expect problems when using them.