Does this mean that it could be included in the lightbox plugin and have it uploaded to spartacus? Imo it has a much nicer look than the the other lightbox scripts.prettyPhoto is totally free to use, it is licensed under Creative Commons Attribution 2.5. So you can use it in all you projects even commercial ones. Please note that if you plan to make money using prettyPhoto, donations are more than welcome.
I have it running on my site at the moment (using serendipity_event_lightbox) but I'm unsure if I have either the latest version of the lightbox plugin or prettyPhoto. If it can be included and uploaded to spartacus I'll go over the files and make sure they're the latest version.