It is believed that Malbolge is not Turing complete, which is probably the main reason that no Malbolge programs have been written.
The perpetrator has recently implemented an evil little brother-type language (I'd say extension, but it isn't like Malbolge at all) to Malbolge, called Dis (named after the city at the center of hell, according to Dante). In the words of the author, "Dis is like Malbolge, but, instead of attempting to be the absolute worst programming language ever, simply tries to walk the fine line between inhumanly difficult to use and actually impossible to use.".
Personally, I (dis-)like Unlambda better.