Abstract apertium-cy (http://www.cymraeg.org.uk) is a rule-based "gisting" machine translation system for Welsh to English, with both engine and data released under the GPL. We summarise the development of apertium-cy, evaluate its output, and discuss the advantages of a collaborative development model combined with rule-based MT for marginalised languages. e Apertium platform apertium-cy is a "gisting" machine translation system for Welsh to English, based on the Apertium machine translation platform.¹ e platform was originally aimed at the Romance languages of the Iberian peninsula, but is now being adapted for other languages (such as Basque, and languages from the Celtic group -Welsh, Irish, Breton), with much of the work on new languages being pursued by volunteers, following the increasingly common collaborative development model used for free² and open-source soware. Apertium is licensed under the Free Soware Foundation's GNU General Public License,³ and all the soware and data for the 17 supported language pairs (and the other pairs in development) is available for download from the project website. Apertium follows a shallow-transfer approach, and is very fast. Finite-state transducers