Tohu is an engine built on Drools to create dynamic UIs. It is an alternative to the traditional MVC approach which instead uses a generic UI layer to render arbitrary UIs defined using simple business rules.
Most forms have some sort of dynamic behaviour where the value a user types in one field affects whether or not to show another field. Tohu makes this sort of thing extemely easy to build and maintain. Typically you can have the logic of your forms (and page flows) working within days or even hours, and then someone with a different set of skills (e.g. CSS / UI design) can make it look nice.
The initial UI is web-based using JQuery but the plan is to extend this to other UI technologies as well.
For more information (including links to SVN, Jira, and the mailing list) see the main project site at http://jboss.org/tohu
UPDATE 30 March 2014:
Tohu is now compatible with Drools 5.6.0 and Drools 6.0.1. See Tohu - FAQ for migration information.
UPDATE 2 June 2014:
Tohu version 1.6.1 released. This contains a few bug fixes, no longer explodes the tohu-jquery-client jar into the project source folder, and provides an alternative mechanism for specifying the rules when using multiple questionnaires.
See Jira: https://issues.jboss.org/issues/?jql=project%20%3D%20TOHU%20AND%20fixVersion%20%3D%201.6.1
Other useful pages: