I agree that getting old versions should be easier - especially if you bought the latest version.
My experience has been that the problem is mostly "copy protection" schemes. There are various tools to administrate them, and helping somebody with really old software can be a PITA for them. If you are a legit owner of that old version, they might feel obliged to help you despite the trouble. Otherwise, they find it worth their while to minimize those annoyances. For example, if you called Apple and tried to get them to help you with your Logic 6 XSkey authorizations, most of them would have no idea what you are talking about, or what to do. Even simply generating a new serial number for ancient software could be prohibitively difficult.
I have some legit OS 9 software that I spent a fair amount of money on, and when I've called the developers for help after 2010 I hear the wind go out of their sails. Many companies will try to help up to a point, but if they need an OS 9 machine themselves, or some ancient version of PACE or whatever, then they eventually withdraw support. Perhaps not because they want to, but because it is simply not practical.
So, the solution IMO is to avoid using "copy protection"! Then your software works forever, and serves as a testament to your awesomeness.
I have used the Waldorf Edition 1 on OS X, but not on OS 9. I paid Waldorf to upgrade from my OS 9 versions of PPG Wave, Attack, and D-Pole. They were only available separately back in the day (IIRC through Steinberg). These and Koblo Studio were my first real-time software instruments.
Semi OT: There is another little-known Waldorf VSTi - the Terratec Komplexer. Unfortunately only for Windoze, there was supposed to be a Mac version which never materialized. It's a decent synth, basically a native version of the Microwave. I still use it on my Linux setup.