Apertium is a free/open-source machine translation platform, initially aimed at related-language pairs but expanded to deal with more divergent language pairs (such as English-Catalan). The platform provides

a language-independent machine translation engine tools to manage the linguistic data necessary to build a machine translation system for a given language pair and linguistic data for a growing number of language pairs.

Apertium welcomes new developers: if you think you can improve the engine or the tools, or develop linguistic data for us, do not hesitate to contact us.