Sorry you didn't get my point so let me try again.
I purchased that software back then. It worked beautifully. Then it didn't. Why do you suppose that was? Maybe because the software developer(s) wrote some code basicly saying: "OK, you bought this but we're not going to let you use it forever even though it could if we didn't add this bit of code. Get over it."
I own a box camera that is over 80 years old that still takes beautifull pictures.
I also own a Mac Pro circa 2007 running Snow Leopard 10.6.8. It too works beautifully but won't run CS3. It does run AE CS4, Final Cut Studio and many other "older software".
Don't know about you but I'm past 70. Imagine how I'd feel if the doctor told me I'm too old for a new heart. "Get over it".
Hope you get my point. All the best.
Remember to put your mask on before leaving home. :}
It sound like you miss the life raft Adobe through you. You did not grab hold of it to download a newer CS3 Installer that does not require activation for CS3 version it install with your new CS3 serial number you received with the download when you provided your old CS3 serial number. Adobe no longer provides any support for Old 32bit applications. New Mac computers do not support 32bit Application. New Apple Processors can not run X86 code. And not all X86 code can be translated into code for Apple ARM processor and macOS. Thing do stand still and you are responsible for maintaining you machines and software. You missed Adobe life raft. I'm past 80 I did not miss Adobe Life Raft so I can install CS3 on Windows PC. If you have old Mac hardware and software that can run 32bit CS3. If you had grabbed Adobe's life raft you could install CS3 on that old machine. However, You original CS3 installer requires CS3 Activation that services no longer exists. You did not keep your CS3 Up to date. You miss Adobe's CS3 life raft. Can you use your box camera on your old Mac or new Mac.
CS2 can no longer be activated it too had a Life Raft
I have the CS2 and CS3 new installers and serial numbers. Now I'm past 80 and can no longer download these newer versions so I keep them well backuped. On rare occasions I will use CS3. Cs2 does not run all that well on Windows 10 so I do not use it. Photoshop 2020 IMO is the best version of Photoshop that I have installed.