In order for kppp to run correctly as a user other than
root, it needs to be setuid root. I don't know of any
security problems with doing this-- doing a 'make install'
from source makes it setuid root, and it's also that way in
the official KDE packages for RH52.
KPPP has not been through a security audit. We do not ship SUID
non-security audited programs.
You may set it SUID at your own risk.