You are correct. The older H3 version is no longer commercially available. However, that does not mean that it is 'abandonware'. AGSI, the company holding the development rights, has not relinquished any of those rights. Some folks over at one site tried to post the *.exe files for Harpoon3 and were immediately ordered to cease and desist.
Just because the company does not wish to support or offer a certain version of their software, does not necessarily mean that they wish to abandon it. If only they would...

Since you still have access to Harpoon 2, you might like to try out our scenarios. I'm pretty certain that they will still run in that version.
Harpoon3.6.3 users can get the:
Complete Harpoon 3.6.3 Library