Hello,
I have created an example plugin that demonstrates how to provide custom language packs and localized labels to the Morpheus UI: GitHub - cpdtaylor/morpheus-localization-pack-plugin-example: An example Morpheus plugin for providing new localized messages that can be used within the UI and Catalog Forms
This will help you if you need to provide Forms in Morpheus that can be localized in multiple languages depending on the Users locale preferences.
In my example I even ensure the Form can be localised in Klingon! 
If you are looking to translate the out-the-box Morpheus UI messages, please consider contributing to our translations via our localization process: Morpheus Internationalization & Crowdin Customer Facing
Thanks,
Chris