Couldn't we use that latin motto by St Agustinus as slogan ?. Possibly with a translation to the language the page is written on. I guess that's already considered and discarded, so we should think something else.
I can't think of much. What about
Let freedom grow on software, let software grow in freedom.
?
In fact it doesn't say much beside the Free Software Foundation Europe name itself, so it may not be very useful. By the way, whether it is useful or not, is it proper English?.
On an unrelated point. I want a t-shirt (at least one), with the map, Europe riding the gnu and the latin motto (not this one). Who should I contact?.