Mira
You don't need a license as long as the application you're building is for evaluation or testing, and NOT for production use.
You will need to purchase a license for production use.
Licensing can be complex, and you should contact your local Adobe office or enterprise partner for details.
XPAAJ was never free, it was bundled with other Adobe products.
It has been deprecated, and is no longer supplied or supported, as far as I'm aware. You will need to purchase a LiveCycle license of some sort.
Howard
http://www.avoka.com