It's a bit of a struggle to find useful info on the site.
According to the site WILL (Wacom Ink Layer Language) is a new standard for digital ink (they mention 'open' without defining it) which is better than InkML or other competing formats. This link [1] has some decent info.
1 comment
[ 0.23 ms ] story [ 10.4 ms ] thread[1]: http://will.wacom.com/get-started.html#c109