In my opinion it would be great to have the latest versions of Smack in the central repo with a proper pom.xml and a source artifact - whether or not the build is actually done with Maven.
I would also recommend the Maven dir structure - it’s not that demanding, after all.
Once you have Maven’s pom.xml set up, Maven can generate Ant script doing the same as maven. But naturally, this has some limitations (not all maven plugins exist as Ant tasks, etc.).