Having looked a little further I now discover that using Tamil as a source language is not an option. I would have thought as language translation is a two way thing it might be an idea to allow any of the languages on the site to be used on either side of the learning experience.
I do not mind so much if it is not possible to translate the interface into another language but it would certainly be handy for anyone who is advanced enough in English that they were able to use the site if they could use it from the point of view of coming from their native language.
I have students whose English is quite good enough to find their way around the site and they would love to contribute but without being able to change the source to their language it is all a bit skewiff; they don't need to learn their language, they need to learn English. Admittedly they are not wholly barred from just reversing the words but still, it would be nice.