The 'juicebox.js' and 'juicebox.php' files do not change from gallery to gallery.
The 'pswd.php' file contains the password for a gallery (if you choose to password-protect it).
Please see the Password Protection support section for details.
If you do not want to password-protect your galleries (or if you are happy to use the same password for all your galleries), then all your galleries can share a single instance of the entire 'jbcore' folder (rather than having an individual 'jbcore' folder for each gallery).
If you'd like to do this, then please see the Using an External jbcore Folder support section for details.
Essentially, all you need to do is upload a single 'jbcore' folder to somewhere on your web server and make sure that the 'juicebox.js file (from within the 'jbcore' folder) is loaded via a <script> tag on every page which contains a gallery.