You can indeed purge any package with "apache2" in its name. I have no Web
server and none of those packages are installed on my system. They are not
part of the default install either. I guess you either explicitly installed
Apache or some package depending on this Web server. That is why, before
confirming the removal, you had better check whether this removal does not
trigger the removal of applications you actually use.
I do not know why the init script remained after the deletion of the
"apache2" package. Executing the following command would stop the init system
from trying to start/stop Apache:
$ sudo rm /etc/rc*/*apache2
It is about removing the symbolic links to the apache2 init script (not the
init script itself... although it should not be on your system anyway!).
