That's true, I did not talked about it in the English forums because it's not the case with http://www.google.fr/search?q=phpbb+seo&hl=en
The interesting thing to notice in the french site links is that they include sub domains.
This illustrate the way Google is dealing with them, treating them as part of the main site for both of them, not being the oldest only (telechargement.phpbb-seo.com (the french download is not as old as the french directory for example).
About the English world result, we'll see, I already saw some web site with site links in more than one language, but mostly with the same site links in all case.
Will Google make a smarter selection and grab the corresponding English pages and sub domains ?
Would be great