AHA! Found a workaround for this issue!

If, for whatever reason, your unarchived version still has com.apple.quarantine xattrs on the dir (or executable presumably), it will cause GPR to occur regardless of whether it is located under "/Applications" or wherever. Not sure how that's possible, as Apple says GPR shouldn't occur in those cases, but clearly it CAN occur.

WORKAROUND: The way to fix the problem (after moving the directory under "/Applications", haven't tested elsewhere) is to then issue the following cmd via terminal:

> xattr -c -r /Applications/Blacksmith3D-v6.2.0.0-Mac

After issuing that cmd, and confirming all xattrs were gone (using "ls -al"), I was able to execute and register Blacksmith3D fine, and it appears to operate normally. I can't speak to the security situation of doing what I've suggested, so use at your own risk!.

Hopefully Apple and developers can work out a better way to manage GPR than the current one, which appears to behave fairly unpredictably. I'm not holding my breath, however.