I'm afraid i didn't like very much sbillard's approach to the problem.
First of all because it make no sense to say "if you don't like the plugin then just do not use it". Of course the same can be said about zenphoto, that I like indeed very much, so what's the point? He feels I offended him somehow? If so it was not my intention, and I apologize again for it.
As far I understand from your explanation this compromise is just adding the lang prefix to generate a sort of 'fake' navigation inside zenphoto for web crawlers. My point was, and remains, that for that 'fake' URl was indeed enough the sitemap with the lang prefix. The side effects introduced by the new rewrite_path function are not acceptable imho in change of (probably) nothing.
Before we were "cheating" just in sitemaps, now we are "cheating" all over zenphoto, at the price to have 302 redirects for every link.
The subdomain approach is of course much better, and I'll try to setup my site for that, however I still think that was better to live things as they were before for people not using subdomains.
What else, I understand that you are doing a wonderful and hard job on zenphoto, and that you are may be under pressure for the next release to come.
So, sorry for sharing my opinion with you if this is somehow irritating someone of you.