I've tried to simulate this issue but no success. What I did was:

1) Download and Extract Forge 2.8.1.Final http://forge.jboss.org/download.
2) Remove ~/.forge directory.
3) Enter Forge Shell
4) Install PicketLink Addon with the following command

addon-install-from-git --url https://github.com/picketlink/picketlink-forge-addon.git --coordinate org.picketlink.tools.forge:picketlink-forge-addon

5) Follow steps as described at "http://forge.jboss.org/addon/org.picketlink.tools.forge:picketlink-forge-addon", Section "Applying Security to a Forge Scaffold Project"

I really would like to get this working for you. Maybe we can chat on #picketlink at IRC Frenode, if you like to.

Thanks for all feedback.