1.50 is the same as 1.40 but with additional resources, the user named "emumanu" translated the rest, so you need just to add the extra xml after install 1.40 and you get complete 1.50
Before install 1.40 read these posts, maybe you'll need cut into small files the 1.40 xml if you get timeout uploading problem and additionally you have to fix a couple of lines because the xml is bad formed in 1.40 and fails with 1.50 versions:
https://www.nopcommerce.com/boards/topic.aspx?topicid=3947 (timeout problem)
https://www.nopcommerce.com/boards/topic.aspx?topicid=3622 (bad formed xml problem)
If you need the extra xml send a private message with your email to me or emumanu user and we'll send you the file, it's too long to post in the forum. Or if you prefer download it from my mediafire account: http://www.mediafire.com/?w1y4omtjwez
I hope it helps.