On retrouve plus ou moins les memes choses entre Yahoo et le couple prototype/script.aculo.us la seule différence notable se porte sur la documentation, celle de Yahoo est beaucoup plus claire et regroupé sur un seul et meme site : http://developer.yahoo.net/yui/
La librairie Yahoo ! peut se décomposer en 2 parties : le core et les controles. Le core quand à lui possede plusieurs parties :
The Yahoo! UI Core Utilities simplify in-browser devolvement that relies on cross-browser DOM scripting, as do all web applications with DHTML and AJAX characteristics.
Animation: Create "cinematic effects" on your pages by animating the position, size, opacity or other characteristics of page elements. These effects can be used to reinforce the user's understanding of changes happening on the page.
Connection Manager : This utility library helps manage XMLHttpRequest (commonly referred to as AJAX) transactions in a cross-browser fashion, including integrated support for form posts, error handling and callbacks.
DOM:The DOM Utility is an umbrella object comprising a variety of convenience methods for common DOM-scripting tasks, including element positioning and CSS style management.
Drag and Drop: Create draggable objects that can be picked up and dropped elsewhere on the page. You write code for the "interesting moments" that are triggered at each stage of the interaction (such as when a dragged object crosses over a target); the utility handles all the housekeeping and keeps things working smoothly in all supported browsers.
Event: This sophisticated manager class gives you easy and safe access to browser events (such as clicks and key presses). The Event package also includes the Custom Event object, a mechanism for publishing and subscribing to interesting moments in your own application flow.
En ce qui concerne la license, Yahoo est sous BSD License