Building on the recent offer of a professional spanish translator, I think it is useful to review the status of translations in Stendhal.
Getting the game to be multilingual should be a priority, as it would help to significantly increase the number of users and perhaps to reduce the problem of players leaving the game within the first five minutes.
The most important part would not be to translate the interface, because any player can make their way through it and handle a limited set of nouns or verbs. The hardest part are the complete sentences and extracting meaning from a text with grammatical constructions. In this sense, the most difficult obstacle for non-English speaking players would be tutorials and quests.
The most time-consuming part for multilingual support would not be the translation itself but the previous step to it which is to mark translatable text strings throughout the code. In fact, the role of the translator should be simply to translate the phrases that appear for example in a text file without having to find them previously throughout the source code.
This task should be avoided in the future by having the discipline to create new content by marking from the outset the translatable strings that may appear.
It should also be used if possible any software which assisted specifically in the activity of the translation and the management of the various versions of the translations (e.g. something like narro https://code.google.com/p/narro/ as suggested by javydreamer)
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Tutorial events could be a good candidate for translation. They're all in one place so it would not be difficult to find and mark them either.
Quests are an order of magnitude harder problem, because they use dynamically generated sentences. That would need language specific Grammar in addition of translating all the individual bits, and it would still fail to due to languages differing in structure