How can I set up a language filter for Minecraft?

The Question comes down to is it textual language, or spoken? If it's textual then I'm sure it's possible! This mod will solve the issue. That is if you can get the admins on the server to install it.

If it's spoken, I either suggest asking them to play without sound either via minecraft it's self or the client being used. I don't know how to do this though. As a heads up, the two main VoiP (?) services are mumble and teamspeak.