I did some investigation a while back, and it seems that my version of the Microsoft compiler does not support IPv6. This isn't too surprising, it is about 15 years old.
However as discussed in another thread a while back, I am reluctant to shell out over $2000 to upgrade. From the Microsoft web site "Buy from $2,084".
Compare this to Apple which uses gcc/g++, and they offer the full development environment for Apple, iPhone, iPad etc. for no charge (and around only around $100 per year it you actually want to sell through the Apple Store, something you are not required to do for normal apps).
And compare to gcc/g++ which is free for Unix, Cygwin, etc.
And avr-gcc which is free for microprocessors like the Arduino.
I am giving MUSHclient away, I receive a small number of donations, basically barely enough to cover the cost of keeping the web site up, if that.
So what can we do? Well I am guessing that people will have released some sort of proxy/tunnel that will let you convert IPv4 at home into IPv6 on the Web. Google for "ipv6 proxy" and you will find a few.
This would, or should, operate similar to a SSH-tunnel. That is, you connect locally to your tunnel program using IPv4 (ie. using MUSHclient) and configure it to forward onwards using IPv6 to your MUD. This page describes how stunnel works:
http://www.gammon.com.au/mushclient/stunnel.htm
Now that is for SSH, and not IPv6, but I don't see why something virtually identical should not be usable for IPv6.
If anyone finds such a thing, please let us know.
My problem would be that I doubt my router supports it, and I don't know about my ISP either.