Not much here. In ppp/ and pptpd/ you'll find a patch called
syspath which will be useful to you if you are creating an ASP
type VPN box with unique pptpd and pppd configs for each customer
sitting behind a linux box.

An alias loopback interface should be created for each VPN end point
and each customer will connect to their unique address and authenticate
against their own unique user list.

Under wanpipe/ you will find my rendition of their RPM. 
Sangoma does/did not release a source RPM but were kind enough to give me their
spec file when I asked for it. Unfortunately it did not use a build root and
expected to find a lot of files pre-existing on the build host.

I had to extensively hack the spec file and the Setup program to get an RPM 
to build. I have sent these changes to Sangoma and hopefully they will use 
at least part of my changes to re-release their RPM.