This is my learning diary: I am a web developer in Madison, Wisconsin. I used Beyond Compare for a year and kept track of what I learned.
Beyond Compare is made by Scooter Software. They have a comprehensive site where you can buy BC, read the docs, or contact the support staff.
At the official site of Beyond Compare you can download the software. It runs fully featured for free for a couple of months in normal use. A Standard license of the current version is $30.