OK, since this keeps cropping up I'll try and give some clear, definitive answers (AIUI):

No 2005 OS application will work on the 2006 OS (due to a move to the EABI)

No 2005 OS package will work on the 2006 OS (due to a move to proper package management).

Putting stuff in /var/lib/install on the 2006 OS will have no effect (due to extra applications now being stored within the root filesystem "proper" - a side effect of proper package management).

Yes, all the applications in the ApplicationCatalog will have to be either rewritten, reported or recompiled. Command line programs should just need recompiling and repackaging; GUI programs have a slightly new (but much better) API to use.

HTH,

Andrew