I received and email from the MacHeist directorate today. The controversy has been solved by YazSoft offering a free upgrade to Speed Download 5 for MacHeist customers, but only for a very limited time - March 13 2008 until March 27 2008.
It is nice that I got the email, albeit 5 days after the offer was extended.

This list of changes that come with SD5 are available online.

So if you purchased Speed Download 4 with MacHeist II, and choose to upgrade, then proceed to yazsoft’s website in a quick and orderly fashion to get the upgrade offer.