No, you don't need to. Just switch to downloading the Mac versions and you should be good to go.

No, you do not need to repurchase the games; one purchase includes all three (if available) platforms for the game.

You can also filter your library by OS to see what games you own already work on Mac.

A Mac is still a PC though.

Yeah.

Mac is still a PC, as was told before. Yet... No, you don't have to.

But if a game has only Windows version there is little you can do about it. You can always purchase a Windows copy and install it in Bootcamp or so I've heard. This way you will not lose almost all of your library (it kinda undermines the whole idea of Mac usage but if you are OK with Windows on Mac hardware then it is a good start for slow and comfortable moving towards full time MacOS usage).

Thanks all! I was kind of hoping that, at least the Myst-type games would have made the jump (I figured that NWN and others would be a bridge too far.)

Perhaps I can get something WINE-like to work.

And, yes, a mac is still a PC, insofar as an android device is a personal device that you might use for computing...

Maybe some interesting links for you to run windows games on a mac

Porting
http://paulthetall.com
http://portingkit.com/en/

Wine
https://www.codeweavers.com/products/crossover-mac
http://wineskin.urgesoftware.com

Virtualization
http://www.parallels.com/de/
http://www.vmware.com/products/fusion.html
https://www.virtualbox.org

Paul the Tall is someone who created and creates wrappers to let windows programs run with Crossover or Wineskin on a mac. You don't need a virtualization software and a copy of windows for this. He also created a client called the Porting Kit, which helps you to download and install the important stuff and make game installation very easy. He is very active and often tries to offer ports for newer gog releases. He is also open for requests.

Talking about Wine, Wineskin is a free porting utility using Wine. It's free, but tricky to use. A good GUI and complete package for Wine is Crossover, which is unfortunately not free.

And then there are of course the virtualization programs, which lets you install a windows copy in a virtual machine. Top dog was and very likely still is Parallels, which has a very good 3D hardware emulation. The performance if you would boot with bootcamp a native windows, but still very impressive and for many games enough to avoid a reboot of your system. In recent years VMWare started to heavily to improve Fusion, which is regarding tests now very close to Parallels. Both are not free and costly. Keep here in mind that like Crossover you need to upgrade the software every year, as Apple will release MacOS major releases every year that often makes trouble with older program versions due to heavy under the hood changes. If you just want to play some very old games, you maybe want to give Virtualbox first a shot. The 3D graphics performance isn't as good as Parallels, but maybe enough for some low-demanding games.

So, my recommendation would be first to check out Paul the Tall site and his free Porting Kit. Otherwise Bootcamp is a good option if you don't have a problem to reboot your system for gaming.

No, your analogy is wrong. Mac is as much of a PC as a PC with Windows, Linux or any other OS is.

I have had many good experiences with PaulTheTall’s wrappers in the past, but I do not recommend their wrappers anymore since they started to force this abysmal PortingKit application down your throat just to download them. I encourage you to get familiar with Wineskin Winery and Wine, many games will work out of the box when you use a WS9CX* engine. Check out https://appdb.winehq.org as well, where people report what they had to do to get a game working.

wineskin and cider wrappers:
paulthetall,
portingkit,
portingteam,

application to port that use win but not wineskin:
playonmac,

to use wine on mac:
wineskin,

of course you can also use a virtual machine (virtualbox, vmware) or bootcamp, but you need a windows license.

and there are still many native games (66/106 on my library are games with an official port).

I think the only thing missing from other post is
http://portingteam.com/

where there are lots of really good and unique port like dragon age origins.

Again. thanks everyone! I hadn't thought about virtualization, which is kind of funny, as I use it all the time. My main concern there is the sandboxing, and loss of access to lower-level systems between the "box" and my machine. But, hey, I have time to kill this week, and all of it will be fun!

I really do appreciate the positive support, and with only a couple of trolls that had no value to add... ;)

You have my sympathy...

Despite editing your post, I still got the notification that you mentioned me in a post. So it's pretty obvious you meant me and the others who educated you about the fact that Macs are still PCs.

Educating someone is not trolling, so just because you don't want to admit the truth you shouldn't label us as trolls, becauset that's what real trolls do (and sore losers who don't want to admit they were wrong). Either say why you disgree or don't comment at all, otherwise you're baiting people like a true troll. Also this information was very much on topic since you might use it in the future.

Given the fact that you weren't able to find out whether you can play GOG games on your new PC on your own shows that your opinion on whether Macs are PCs or not has zero value on this matter anyway, especially given that the very first sentence about them on Wiki proves you wrong. And yes, it's right, any IT person worth their salt will tell you this. Just like no one disagreed here but three random people jumped in to confirm that.