Sprout Forms: Localized version of form with translated labels?
Currently, Sprout Forms (v1.1.0) is translatable, but we have not yet added support for Craft's localization feature.

You can find a template of a translation file on our Github Account.

We want to support localization in the long run. The main reason we have not yet is mostly just one of priority. In comparison to other advanced features, we have had very few requests for it (feel free to send us a note and advocate for how this needs to work for you) and development for it isn't documented anywhere (feel free to send Pixel and Tonic a request for documenting it better too!). At the time of this posting, I posted a question here about the topic 7 months ago [February 2015] and the question has received one upvote and 41 views:

How do you add support to manage content in multiple languages in a plugin with a custom Element Type?