for source codes by other authors u should ask them directly. 

alternatives similar applet that i made
Ejs Open Source Creative Commons Attribute Projectile motion Java Applet
http://www.phy.ntnu.edu.tw/ntnujava/index.php?topic=745.0
has the source codes for sharing under license attribution.

u could do a search for "projectile motion" in this forum and u will find a couple more :)

enjoy!