Free alternative to Prototip?

I'm redoing the tooltips on a commercial site and am looking for a good tooltip library to use. Some of the pages use prototype already for other functions, so I need to find something based on pr开发者_如何学编程ototype that can do the following.

1. Dynamic positioning, meaning if the tooltip would fall outside of the window then it is moved to a better position.
2. Automatic rounded corners
3. Ability to pull content through AJAX calls

The only library I've been able to find is Prototip, which charges for commercial licenses. I doubt my boss would be into $500 for a multi-site license, so I'm wondering if anyone knows of open-source alternatives.

http://okonet.ru/projects/tooltips/ - free, but no dynamic resizing/ajax.. good for something to start with.

http://www.opentip.org

It's free, opensource, and supports everything prototip supports (and more) including dynamic positioning, rounded corners and AJAX calls as well as support for all major frameworks (jQuery, prototype, ender, components and no framework at all).