I'm just wondering out of curiosity wheher anybody anywhere has managed to keep Poser 7 or Poser 8 running ? If so, then Mac or Windows. And more importantly, how ?

I'm 99% certain that Microsoft's IE10 killed Poser 8 back in Oct 2013, although it was possible to keep Poser 8 running by blocking the IE10 update, but I think even that stopped working when IE11 hit the fan.

I have no idea about Poser 7 because I never owned it.

(P.S. I've never, to this day, had any problems getting Poser 6 to run on any computer !)

Poser 7 was very much like Poser 6 and it still works for me, not that I use it much. It's only for checking when someone here asks a question about it. Once Poser 8 started having the problems you mentioned, I gave up on it and uninstalled it.

As far as I know, Poser 4 through 9 will still run on a Mac. I bought Poser 10 for the Mac too, but haven't actually fired it up since I switched over to PCs that year. BTW, my switching from Mac to PC had nothing to do  anything except Apple was getting a little too greedy after Cook took over and kept trying to update the OS. I still use MAC every now and then, but I'm a Windows guy now.

P7 and P7 Pro works on my machine. Win 10 Pro 64bit.  Don't use it much, but when I do, it works.

I have Poser 5 on my oldest Mac (1997) and Poser 7 on my G5 (2005) - still both running and occasionally used.

I use poser 7 on a windows 7 desktop that I keep off line.

Having Poser 4, 5, 6, 7, 8 pro, Pro 2012, Pro 2014 and 11 all working just great and Stable on win 7 and win 10 . all are still in use due the need of different Pythons and addon. Poser 4 render engine can also be useful for certain render results. Poser 4 - 6 are running Portable 7-11 are installed in sequence latest 11 directly in the C root in a Poser Folder. Not in the C program folder as this is causing big issues, original runtimes are set to be in the Poser program folder and not in the Own data Root, this method also ensures that the Installs can be kept Portable without any further issues and conflicts with further Libraries and Python collections that are individually made for the Poser versions. If you still want to use Flash library you need an older flash version and IE with Flash that should make the trick else using the Air Floating version less complicated solution. 

For me Poser 7 works on Windows 10 as portable.  I didn't need to install it.