AdWords API Re: Does Google allow development

Detecting what version of code library someone is using to talk to
their
system based on user-agent string the client is sending would be
ridiculous.

If they really wish to guard access to the API and make some sort of
commercial
program, they would need to support official client libraries for every
platform out there.
Also then what's the point of using SOAP. Just throw some propriatery
communication
layer that only your client library understands.