You can get it from Qt-apps, here:
http://qt-apps.org/content/show.php/Auralquiz?content=139127
Or from Gitorious, but the source in Gitorious might change at anytime, so for v0.5, it’s better to get it from Qt-apps.org
Also, if you’re a Slackware user, somebody from Slacky.eu prepared a package:
http://www.slacky.eu/asche/pkgs/index.php?ver=15&pkgname=auralquiz&pkgver=0.5
Thanks, Gohanz!
Speaking of provided packages, an Archlinux user created a PKGBUILD in AUR for Stressitout, here:
https://aur.archlinux.org/packages.php?ID=50274
Thanks, Unikum!