Smack 4.4.0 source isn’t tagged on the repository nor has a release on GitHub. I have experienced previously GitHub not showing tags on their branch/tag selection widget, but https://github.com/igniterealtime/Smack/tree/4.4.0 is error 404.
I think there hasn’t yet been any commits towards 4.4.1, so https://github.com/igniterealtime/Smack/tree/4.4 should still correspond pretty much to 4.4.0.
Thanks for reporting this. I have pushed the 4.4.0 tag.