MediaWiki is the software that runs Wikipedia. Within the Wikimedia Foundation it is used in many languages for many projects. Some of these projects, like the Bengali Wikipedia, are the biggest single source for a language on the Internet.
The BetaWiki project has become the hub of the MediaWiki localisation, not only is a Web interface provided, there is also support for "gettext" or ".po" files. This allows for the use of CAT Tools like OmegaT. Managing the localisation of several hundred languages is not easy and making sure that MediaWiki is properly localised is a struggle. We found that the quality of the language support is spotty. Policies in the WMF have changed requiring localisation as a precondition for a new project. Big improvements in the MediaWiki localisation have happened in the last few months.
In order to improve the MediaWiki usabilty we have received some funding from Hivos. This will make it possible to put a premium on the localisation of MediaWiki for languages not in Europe or North America.
Many of the languages that MediaWiki supports are different and we do get requests for changing the sort order. Typically we follow the CLDR but there are languages where the CLDR does not help us. It would be good if we knew how to work with the CLDR and share our work.
For American Sign Language, we have been told that for SignWriting an extension will be programmed allowing for a Wikipedia in sign languages. This we hope will stimulate the emancipation of all sign languages a lot. It will be a first to have encyclopedic content for sign languages.
NB today new Wikipedias are starting in Saterland Frisian, Crimean Tatar and Lower Sorbian. :) For many more languages preparations are being made in the Incubator. :)