This extension helps you set multiple urls for every product/category/brand/info (one for each language).

How does it work? If you have a product called Product in EN and Produkt in DE - it can have 2 links: one for each language:
http://yoursite.com/product.html - for EN
http://yoursite.com/produkt.html - for DE

Language is detected from the link and it will be automatically set for user. This extension doesn't generate SEO URLs. To generate SEO URLs, use it with Professional SEO URLs or use entire Opencart SEO Pack PRO.

No files or data will be overridden. Easy VQMOD install.

Demo:
http://ocdemos.womgoo.com

Admin area:
http://ocdemos.womgoo.com/
user: demo
pass: demo

UPDATE:
Sitemaps were added for each language. They can be found in Extensions -> Product Feeds -> Google Sitemap and contain all SEO URLs for that language.

Multi Language SEO URLs allows you to set a SEO URL (SEO Keyword) for each language, but it won't automatically generate SEO URLs. If you want to automatically generate multi-language SEO URLs you'll have to use Opencart SEO PACK PRO

This extension is included in Opencart SEO PACK PRO. It contains 20+ SEO related extensions and you can save more than $150 by purchasing the full Opencart SEO PACK PRO:

http://www.opencart.com/index.php?route=extension/extension/info&extension_id=6182

*** This extension is not compatible with OC 2.x. The version for OC 2.x and OC 3.x is included in Opencart SEO Pack PRO which also includes all the other SEO related extensions and features.