It was added on 5 November 2007.
Following feedback and questions on the Forums, we wanted to clear up some worries that you may have.
The Assist System is designed to be a safe and convenient alternative to obtaining aid via the trading system. Before, if you had a willing high-level friend, you could do everything that the new Assist System offers. The difference now is that you no longer run the risk of an unbalanced trade!
If you can find someone willing to give up their time to help you fish, then they would surely have been willing to give you the fish previously and the Assist System is no replacement for putting in the work and levelling-up yourself.
For clarification on these points and many others, head to the Knowledge Base article here - after all, we're here to assist you!