You can use Jetpack in the language of your choice and suggest new translations using GlotPress, our translation engine.
Once you have installed WordPress in your own language, Jetpack will automatically switch to your language if a translation file is available.
GlotPress validators will have a look at your suggestions, and approve or change them if necessary. Once your translations have been approved, they will be included in the next Jetpack release.
I found a missing translation, but I can't find the string in GlotPress
Some Jetpack modules, like Comments or Likes, are hosted on WordPress.com. Thus, you will have to look in the WordPress.com GlotPress project to find the strings to translate.
If you have more questions about Jetpack translations, do not hesitate to contact us!
Thanks a lot for helping us fly Jetpack around the world!