./configure --with-location=PET ; make ; sudo make install
The difference with this command, and yours, is that this one leaves out the slash from PET. Instead of "/PET", it puts "PET".
Yes, the 'make' command is not necessary, really. But the "sudo" command would then generate some files owned by user 'root', while if the separate 'make' command were run, it would generate files owned by the current user.
Two ./configure commands that use the "--with-location=location" parameter, and subsequent installation, would have everything separate, including the database. That is, it won't create a separate database in the "location-one" database, but it would create a complete new database. One database for "location-one", and another for "location-two".
I am not sure what will happen in case the PET subdirectory is already created in the digitalocean droplet. Bibledit-Web is supposed to handle this on its own. If the subdirectory PET would be already there, I am not sure how the installer and/or Apache would handle that. The recommendation is to not create it manually. Another thing is that the bibledit-web installer does not really create subdirectories on /var/www/, but it updates the Apache configuration to use virtual directories, while the real installation does into /usr/share/bibledit-web/location.
Wishing you well pursuing the goal of editing two different translations simultaneously!
Teus.