Here’s a download link to version 2.1 of BeatBuilder by charlesspencer. I don’t think there’s any version newer than this one
Dropbox - BeatBuilder.jar - Simplify your life
If you don’t have Java already installed and running on your computer, you’ll need to download and install it to get BeatBuilder working.
You can go thru the most relevant BeatBuilder thread here: Free MIDI editor designed for BeatBuddy - #296 by dawnpgeo