YAEB Director is written in AutoHotkey which is a freely available scripting language with a utility to convert the script to an exe. It's Windows-only. You can find AutoHotkey at http://www.autohotkey.com/. YAEB Director is written under an Open Source license, the source code is freely available to all to inspect or even contribute and make changes.
The source is here: https://bitbucket.org/SumRandomGuy/yaebdirector
Want to help with development? That's VERY MUCH encouraged! If you make any improvements, please submit them back to me, SRG, via skype or the YAEB forums so I can consider adding them to the main. Not a developer but have a suggestion? Leave a comment below.