General Questions

What is Fortress?
Is Fortress Dead?
No. Fortress 1.1 was just released in early 2004. We are working on a unified Avalon platform (with a single container project) which will mean Fortress, like the other current containers, will be phased out. A migration path will be provided. Until then, current Fortress users can continue using the container without concerns. New users of Avalon are encouraged to consider Merlin before adopting Fortress however.
When should I use ECM instead?
Never. Fortress supports all of ECMs features, is better designed, more extensible, etc. The only reason to use ECM is because you are already using it and don't want to upgrade.
Component assembly in Fortress?
When should I use Merlin instead?
Merlin is not (yet) as flexible and light-weight as Fortress. So if your need is primarily a light-weight container without all the bells and whistles, Fortress may better suite you. If you need a command-line driven (embedding is supported in Merlin, but not the primary focus) server framework, that does automatic dependency resolution, handles central component repositories, enhanced security (under development) and dozens of other advanced features, Merlin is your choice. You can even embed Fortress solutions in Merlin if you like, the other way around is trickier.

Initialization

These jars can be found on a maven repository like http://ibiblio.org/maven