It seems to me that if one wants to define these functions within a project to keep them version controlled and bundled together with the rest of the application (seems reasonable), one might as well directly write the functions directly rather than, say writing a ruby thingy that generates the javascript view functions.

Better to use the full power of CouchDB’s MapReduce implementation (which, as an aside, and as has been noted elsewhere, might better be named “MapCombine” to distinguish it from the flavor described in the MapReduce whitepaper, the difference being that CouchDB requires Reduce functions to be commutative and associative so they can be sliced, diced, memoized and combined) and write your map and reduce functions directly.

Either javascript or ruby would be reasonable choices for a rails or merb project, it seems to be. Either way, I wouldn’t bother to translate it since CouchDB can use pretty much any language natively for this task.