The Google spell check guy has released his non-Google spell check option, Nox Spell Server. It's a server that runs Python and talks, via a local port, to Aspell - his comments:
Nox Spell Server is a little Python Aspell server that is fully compatible with GoogieSpell. If you are concerned over privacy or reliability of Google's spell service, then look no more, because you found your solution Aspell also supports far more languages than Google spell service.
http://orangoo.com/labs/?page_id=72
So this is very cool, and exactly what I was looking for, however it does mean that people that want to use it with Roundcube need to run this as a server/service for Roundcube to connect to. Can we include this in Roundcube, but have it in the config where it uses Google by default, and Nox if you call it out within the config? This way RC will work 'out of the box' but also allow you to use your local spell server, once it's config'd. I'm on vacation, but I'll start looking at this later in the week - would like to start testing this right away, if it weren't for this nice beach outside!
http://fak3r.com - you don't have to kick it