After thinking about this over the day, i think we should leave it as it is. The Reason is quite simple: Since there is no possibility to allow only specific websites (f.e. widelands.fr) to display the forum in an iframe, we have no control about possible other websites doing it.
Vassili: Isn't it possible to use the Feeds for this? Latest posts feed on french forum, Latest Topics feed on french forum Don't know if clickjacking protection is used here also... if it is used we could disable it for the feeds (which should be safe, imho).