I have updated the English to "Simutrans is an open-source transportation simulation game available for Windows, Mac, and Linux. Establish a successful transport company: Build road, rails, channels and more to get passengers, mail, and goods to their destinations." as suggested by Prissi, and updated French, German, Spanish, Czech, Japanese, and Portuguese with the provided translations (so if you browse the steam store in these langauges, it should now show the given translations).
Other options provided by Steam are:
Italian, Arabic, Bulgarian, Danish, Dutch, Finnish, Hungarian, Korean, Norwegian, Polish, Portuguese-Brazil, Romanian, Russian, Simplified Chinese, Swedish, Thai, Traditional Chinese, Turkish, and Ukranian
Translation into any of these is welcome.