The package-key is just that.. authorize-gateway if you are using the Authorize.net gateway package.
Ryan is right that ecommerce will break in 5.3. The ecommerce package uses many procedures that were deprecated in OpenACS 5.1 and subsquently removed in 5.2 (and 5.3). See: https://openacs.org/bugtracker/openacs/bug?bug_number=2324 for details.
So, what's the current status on this module?
I don't care ecommerce or g2 whatever.
I just want to know which version of module can run safely on which version of OpenACS.
Nowadays to me the word "Open" means never ending stories
which starts here & there.