I think the best solution for running old software like Freehand is to have two computers; an old computer for the old software and a new computer for the new software. I just don't think it is realistic for software companies to support an OS from five versions back. I liked freehand a lot too but that was thirteen years ago, at some point you just need to keep the old with the old and the new with the new. If you only use the program occasionally it shouldn't be too big of a difficulty to move back and forth between two machines.
I guess one of the reasons I am against really old OSs is that I would like to see Affinity take advantage of some of the latest features in Mavericks and Yosemite particularly those that have to do with file managment (duplicate, rename, move, revert to, iCloud Drive, etc.) Other graphics apps like Sketch and Pixelmator already have these features so I would like to see Affinity catch up in those areas as quickly as possible but I don't think that can happen while they are simultaneously trying to support Snow Leopard. Pixelmator actually requires Mavericks to run so they aren't doing any backwards compatibility at all. I can see maybe going back one old version but if you do much more then that the program won't be able to live up to it's full potential.