I kind of doubt Pidgin actually falls within whatever Google defines as an insecure third party application: it's more likely that they just don't want you leaving the Google ecosystem. Either way, I wound up hitting my head against a wall recently when trying to get my Google Talk/Chat account setup on Pidgin. The trick is to login into Google and adjust the security settings on your account. Let's start with setting up your credentials on Pidgin; I'll cover where/how to adjust your Google account afterwards.