This is the official YOURLS .pot file to generate and maintain your own translations.

1. Download the translation file template YOURLS.pot
2. Rename it to [your-locale].po, where [your-locale] is typically language code, underscore, country code (for instance in Portugal that would be pt_PT, while in Brazil it’d be pt_BR). You'll find a complete list here.
3. Install a translation tool: it’s nothing more than a text editor capable of reading .po files, showing you the untranslated string and a text box where you type in the translation, and saving a .mo file which is what PHP needs.
   There are downloadable offline tools, such as poEdit, or online tools like TranslatePOT which can even (attempt to) translate automatically.
4. Translate all the strings and save your work; you'll end up with a fully translated pt_BR.po and the generated pt_BR.mo

1. Install the latest YOURLS release
2. Drop your pt_BR.po and pt_BR.mo files in user/languages
3. Add define( 'YOURLS_LANG', 'pt_BR' ) to your config.php
4. That’s it! Play with YOURLS to check everything is fine

When your translation file is all fine, make sure others can benefit from your hard work!

1. Upload your two PO and MO files somewhere on the interweb.
   It's best to use a source control service, such as Github or GitLab: this will make your changes easy to track, your files easy to maintain, and others' contributions easy to implement.
2. Make it clear for users: a directory with clearly labelled files (yourls-1.6-pt_BR.zip for instance) so they know what to pick.
3. Open a pull request on https://github.com/YOURLS/awesome-yourls and get your translation listed!

See https://github.com/YOURLS/awesome#translations

Thanks to LeoColomb - L10n was a low priority feature but he threw his patch at my face :)

License is "Do whatever the hell you want with it".