One person show. Effectively, it is dead since now it became the proprietary toy of its author. The author is entitled to do what he wants with his own creation, however.
Always when an article of this author gets posted on HN there's a Rust fanatic saying how his code does not work and how wrong he is for committing the sin of using C in current year.
Which are both buggy and one of them is abandoned.
> Lem is a new editor written in Common Lisp that has slime "built-in".
"Lem" is not (neo)vim, has Emacs RSI bindings and even if by some chance it included some "vi mode", it would simply be an emulation, not an actual vi editor. Same issue with Emacs using "evil mode".