When you look at the expanded contents below each tool name you'll find a long series of downloadable ZIP files. These are "builds" of the software, with the most recent ones at the top of the list. Unless you are required to get an older version, you'll want the most recent. For example, your GM may be using an older version and will tell you to use "version 1.3, build 56" of MapTool, so you'd want the MapTool download that contains 1.3.b56 in the name.
Click each of the headings below to see all available download links.