However, during the process of searching for the files, I also came across some articles saying that Speed Doubler didn't work on OS 9, and that Connectix didn't have plans for OS 9 support for Speed Doubler. Then what is this Speed Doubler 9 that I got? Could it be malware? I even looked into the WayBackMachine and saw that Speed Doubler 9 was never mentioned on Connectix's website.
The installer runs and the UI is quite similar to RAM Doubler 9's installer UI.
Any clarification on Speed Doubler 9? Was there ever such a thing?
I remember how cool it was back then as well. There would be ads everywhere in Macworld and I really wanted it at the time. To answer your question, I am quite sure there is not a Speed Doubler 9. 8 was definitely the last version. At that time, OS9 machines started having plenty of RAM and we started moving away from RAM utilities. Although it was not very common back then, there is the possibility that it could be malware.
I really wouldn't touch it. Now if you wanted to for fun, you could run an OS9 emulator on a VM over an isolated network. I personally do this for a lot of Windows software potentially malware. I have a separate subnet/vlan that doesn't communicate with my own network. You just really have to know what you are doing.