There are several implementations of Common Lisp that are still being actively developed.

Because Common Lisp is so easily extended, the ossification of the standard is actually a good thing. The stability of the standard means that code written 30 years ago will still work today. Feature updates aren't required, because any desired feature can be implemented in macros and imported as a library.

Well, yes :) And 4GL languages are actively being used to create new business, so who knows what's dead and what's not.

Perhaps the whole programming field is just a bunch of undead things. Sometimes a bunch of living things stumble upon the field, but they're soon infected...