Why would Yahoo give their code away? Well, over time dynamic web applications will evolve towards a standard way of implementing functions like drag-and-drop, right click functionality, use of maps, etc. Take it a step further: the technologies used for functions will also standardize. For example, Adobe and Microsoft have a huge stake in whether sites use Flash, AJAX/dhtml, or Java to build photo galleries. Since web interfaces now have functionality equivalent to a computer operating system GUI, the UI library helps reserve Yahoo's space at the table where user interface standards for all of computing take shape.
In addition, what if Yahoo's code makes it very easy for the Yahoo search crawler to index dynamic content? Perhaps they could gain an advantage over Google. I have no idea if this is true, but if it's occurred to me, I'm sure Yahoo thought of it too.
If you run a business website, the Yahoo UI code is worth your time because:
- It's the results of Yahoo usability testing, and your users may already be familiar with the UI from Yahoo properties.
- It's stable and maintained by Yahoo for user agent (browser) compatibility.
- Best of all, it's advanced Web 2.0 code for free.
However, Yahoo's open source UI future is unclear. The outline listed on the companion site, Yahoo Design Patterns, shows many items still empty of content a year later. There could be a number of reasons for this -- after all, building out the library takes resources, and it does not generate revenue. Yahoo probably can't afford to make the UI library a high priority. (I wonder if they have tried licensing their code to Adobe or Microsoft, for inclusion in Dreamweaver or Expressions?)
Another major reason for the slow updates might be that only about 500 websites are using the code, according to Yahoo's Gallery site. Many of these are only using Yahoo tech, like site search and maps, as an extra plug-in without really integrating UI code into the website.