Translation and localisation is important in general, because it allows people who do not have knowledge of English to use computer software. MediaWiki is used for example to run Wikipedia in many languages, and therefore translating MediaWiki directly helps people to access free knowledge in their own language.
Here at Betawiki we build and continuously improve infrastructure for easy localisation of MediaWiki. You do not need to know a programming language. If you are familiar with MediaWiki or just editing wikis, you will have no problems with translating.
MediaWiki is currently used in more than 250 languages, and only a few dozen of those languages are maintained. Betawiki receives updates on more than 70 languages each month. See current status of translations.