What do you mean by any language? If JomSocial and Fireboard work in Spanish it will work in Spanish as well.
See what I will do, it is not some kind of "full integration and interaction". What will happen if you apply this patch will be:
- All links to profiles in FB will go to the JS profile.
- Avatars in FB will be the one from JS.
------ This is almost completed
- When you click on send PM in Fireboard it will open the Personal Messaging in JS.
- Registration will be forwarded to JS
- Lost password will be from the Joomla! core
------ This I expect to complete tonight
Now what is more complicated if I would be able to setup in some way the FB signature (this I expect to be easier) and the FB display preferences (this will be harder) in JS. For these two as I am not sure if are possible without significant hacking, I can't say anything as time framework.
Note: All these will hack the Fireboard 1.0.5 RC2 core files (for the moment at least 3 of them).

Edit: The personal messaging can not be integrated (at least for what I am doing) as it is too complicated and for my needs I need a faster solution.