I used the Sakai community nightly server for sakai 2.9.x at this URL
today (July 25, 2012) to verify this problem. I mention this detail, in case it's important to the specific code that was running at that time.
1) I created a Test site. I set the site information language to "French (France)". I added Announcements and one Lesson Builder tool.
2) I visited the site I had created. I looked at the announcements tool to verify that my language was indeed set to French. I received a localized experience in French for the announcements tool.
3) I visited the lesson builder tool. None of the text in lesson builder appeared in French, it all appeared in English.
Looking at the source code, it seems like lesson builder ships with a 'messages_fr.properties' file that should contain localized versions of many strings. One example would be the "Add Text" link. In the default english messages.properties, this is under the key:
in the messages_fr.properties file this is localized as:
however, what shows in LessonBuilder in a French site is "Add Text"