There are tens of open source JSR-168 all of them with their own
weakness and feature.
You may take a look at Exo stack if you are going to deploy a high end
portal system. Officially it does not support  rtl-ltr but its easy to
hack it (matter changing few lines).
In case that you are looking for a easy to deploy and easy to manage
portal, then take a look at StringBeans with out of the box Persian and
rtl-ltr switch support. It is not bundled with tens of Portlet and
themes as Liferay does but its worthy of a try.

I think StringBeans will be one of the first portal with an
implementation of JSR-286 portlet container .


You may find exo at:
http://www.exoplatform.com
and StringBeans at :
http://www.nabh.com