I think this is against TOS! but not confirm!
Do you own all the rights to the software and the rights to sell it?
If you do then it should be okay I think (as long as the buyer knows exactly what they’re getting).
You can’t put a URL to it in your gig description because it’s not one of Fiverr’s approved URLs.
You might get a warning if a link to the website is kept in the gig description that’s not an approved URL.