Drools 5.2 introduced backward chaining and Drools 5.3 made it actually working. I've talked it over with Mark Proctor and he said that he would back-port the fixes to 5.2 for us. This is a bug to make sure we don't forget about it.
Yes, thats my understanding also talking with Mark Proctor. Backward Chaining would be a TP feature in BRMS 5.2. We cannot call it TP if it is broken. Should be backported.
All backward chaining fixes have been back ported. This was non-trivial, as it was a large number of fixes over a period of time.
The fixes were indeed merged. Should there be any fallout, it will be dealt with in other bzs.
This product has been discontinued or is no longer tracked in Red Hat Bugzilla.