It gets regular commits, but I've found it impossible to use practically, somewhat to my regret (I have plenty of use for a LISP that can do .NET interop).
They just got a round of funding this year, and they've got several good talks posted on their homepage about the quirks of working on .NET.
Godot is a decent OSS alternative to Unity, but no Clojure/Lisp so far as I know :(
And somebody made Arcadia bindings for Godot [2], but the project isn't actively maintained. Would be great if somebody picked it up again.
[1] https://www.youtube.com/watch?v=LbS45w_aSCU [2] https://github.com/arcadia-unity/ArcadiaGodot