I would like to make an HTTP/S proxy program to filter/deny certain http traffic based on how I parse the HTTP request in C++.
Is there some kind of starting point code that I can use with an open license for commercial use?
For example if I wanted to do a project on searching I would start with lucene.
nginx is a high performance HTTP/S server written in C that can be used as a proxy.
It has a easy to use module system for which you can write plugins. You should consider using an existing parser like Ragel to help you on the filtering side.
It is licensed under a BSD-like license which is fine for commercial use.