In our AFS environment apache has to be started through k5start to get the right file permissions. However, as a default, httpd detaches from its parent process after the completed startup. This would make it impossible for k5start to renew AFS tickets for the process. The -DFOREGROUND option prevents apache from doing so, and with -b k5start can take care of the backgrounding instead.
If you do not consider this, you may run into "permission denied" problems (see Bugzilla bug 291).