The language used for Haiku development might be English, but that does not mean that end users should need to speak English to use Haiku. Therefore there has been an initiative by developers, contributors and end-users to translate Haiku and its supporting infrastructure into various world languages.
Check out these translation roles we need help with:
You can help translate the Haiku Graphical User Interface into your language at the Haiku Interface Translation website, otherwise known as Pootle. See this introduction to GUI localization guide if you would like to help out with localizations of the GUI.
Anyone with an account at Pootle can suggest a translation for a GUI string, but only trusted "Language Managers" can submit these suggestions to be transferred to Haiku's code base. If you would like to help out in that capacity, please get in contact via the general and language-specific mailing lists.
3rd Party App Translation
3rd party applications can be localized at the Polyglot site. Developers can add their project and upload the "catkeys" of their application. Users can then translate to their native language. See also the forum thread Help translating applications with Polyglot.
If you'd like to help localize existing applications, see the article Localizing an application, that gives an introduction how the app's code has to be changed.
If you prefer to do the translation locally instead of at the Polyglot site, you can download the catkeys and use the CatKeysEditor app (available through HaikuDepot) instead. When finished, upload those catkeys again at Polyglot.
User Guide Translators
You can help to translate the Haiku User Guide into your own language using a simple web tool. It has been developed to keep track of the progress of every language and to ensure all pages are in sync with the original English version. The translating itself is also done with it, online.
Have a look at the translation rules and styles found in the Haiku development wiki for your language. Then subscribe to the main localisation mailing list and the haiku-i18n-* discussion list for the language you want to help translate the User Guide to and then introduce yourself. The respective "Language Manager" will provide you with login information for the online translation tool after your application has been discussed/voted on by the other volunteers. You may have to do a few sample block translations handed to you by your Language Manager.
Start Translating a new Language
If no one has translated any of the User Guide into your language yet, then you follow the step by step process that is listed in this guide.
HaikuDepot Server has an inbuilt tool that creates translations for the descriptions of applications found in the HaikuDepot Desktop package manager app. You will need to sign up to the website via its registration page, then you will need to introduce yourself on its development mailing list in order to get the permissions to translate the descriptions to your language. You can also help to translate the HaikuDepot Server webapp itself by contacting the developers on the same mailing list.