Hi!
I finished the review of the WebYaST development tutorial, which is available at http://en.opensuse.org/YaST/Web/Development/Tutorial . It should be up-to- date and it should be possible to crete a new WebYaST module following this tutorial.
If you find any issues in the document (I don't claim that it is perfect, also it may be just that something is not clear from reading it), please, either report them to me via bzilla or fix them - it's a wiki :-)
Jiri