because aide has hardcoded ${prefix}/etc/aide.conf its impossible to use it since the path is incorrect.
Thanks for the bug report. The conf file is now in /etc/aide/aide.conf. Naturally, you have to edit that file as it is not ready to be used, it is merely a sample. A new version of aide is out, but it requires a new package to be installed which is not currently in portage. Hence that upgrade has been postponed for the moment.
Aide has been upgraded to version 0.8