Ask HN: A non-subscription based live chat service

I've been using Olark for years now, and have recently started to review their services and comparing them to other top-notch live chat services.

I have to say, I don't understand why I need a hosted solution for live chat. It's easy to update and patch on your own and reports could be done via a more dedicated analytics suite using API's.

Anyways, does anyone have any recommendations on a non-subscription based live chat service?

My criteria is finding one that's on a one-time payment model, has desktop notifications for incoming chat requests, and is not Kayako (their prices are too prohibitive for me).

Any help is appreciated. Thanks.