Hi. I have been Mudding for a while now, and have become interested in coding. I was wondering what is used for coding muds, C++? BASIC? PASCAL?

That completely depends on the codebase. If you're writing it from scratch it's completely up to you.
I'd say the vast majority of them use C as their primary language, since most are based off of earlier codebases that used C.

On my mud, there is no code. You just connect, and dozens of full-time Dungeon Masters with world-record typing speed and accuracy type everything manually.

I prefer the opposite route, in which you create an incredibly complex AI and dispense with human interaction altogether.