Hi, and welcome to the forums! well, as noted on the website, sound forge pro 15 is pc only...the versions intended for mac have 'mac' included in the title, ie Sound Forge Pro Mac 1, Sound Forge Pro Mac 2, and the last one made for mac Sound Forge Pro Mac 3...they were all made by sony and are not compatible with anything ios from catalina and after. the only way to use the pc versions on mac would be by using them with the parallels app, or the boot camp apps. you can find a lot of info on youtube about how to set that up. i hope this helps!
As @craig-d has written, Sound Forge Mac will not run under any version of OSX from Catalina onwards, principally because it is 32 bit I understand.
As for running it under an emulator, like Bootcamp or Parallels, apparently this may work but only if your Mac is intel-based and not if it is running any version of the new M1 chip.