I have AD-Aware SE Profesional Build 1501
I am pretty sure that when I got it there was no 3 year license or anythinglike that.
AAW SE V6, Build 1.05 was released in September 2004 - at least, that is when I downloaded it (have just found an old backup copy).
You are correct in that the licensing model was different back then. I purchased AAW Plus back in 2001 - version 5.61 (and Ad-Watch v2.4, as they were separate programs back then). Basically, all of the releases from AAW 5, to AAW 6, to AAW SE, were upgrades to the original technology, and the updates were free.
However, in 2007, Lavasoft released a completely new product, built from scratch to meet the needs of the current, highly-evolving malware. This product requires annual licensing for the Plus/Pro versions - LS have committed to always providing a Free version as well.
When AAW 2007 was released, for a period there was a discount for existing AAW SE license holders to upgrade to a licensed version of the new technology.
I am certain that this discount was only for a few months, however I will PM you with an address where you can check -when you log into the forum, look for "New Messages" in the top-right corner. Never hurts to try