If HTTP is an application protocol, then what's the functionality supported by this application? All the HTTP libraries we've seen before give you access to headers, response codes, methods, etc., which is great--and necessary--but those are protocol details that hide the application underneath.
chaplib is meant to provide that application-level interface, taking care of the protocol details for you (and maintaining unconditional HTTP/1.1 compliance) and letting you work on getting your work done, while still providing enough customization to get the protocol behavior you desire.
What's in a name?
chap = Client using HTTP as an Application Protocol
lib = um, library?