Thanks for the slides (the second link)! What I can conclude is that only the game scripting was ever based on Lisp, never the whole engine? This sounds much less impressive and makes the achieved FPS claims almost irelevant.
And there were some other opinions on usefulness of such approach:
"Despite its advantages, the concept of implementing the game logic in a separate scripting language and writing an interpreter for it was soon dropped (even by John Carmack who had implemented this concept) because of the overall inflexibility of an interpreted language,[3]"
On another side, there are a some games which used Lua for scripting:
As for the arguments that you can't interface with others because they don't know lisp and there aren't lots of libraries that's true of every language at some point in their lifecycle. There might be other reasons that's never happened for lisp or it might just be that no one has successfully made a concerted effort to get it there?
Maybe one of the LLVM based lisps would help a transition or at least let people try lisp on part of their C/C++ code base
"Of the 1.2 million lines of code, roughly 900,000 lines are written in GOAL."
Still that leaves 300,000 lines which were certainly the most low-level and performance-sensitive ones.
The 900,000 lines aren't exactly "the Lisp," but that custom language, developed using the commercial Lisp, but I admit it's certainly an engineering achievement.
And there were some other opinions on usefulness of such approach:
http://en.wikipedia.org/wiki/QuakeC
"Despite its advantages, the concept of implementing the game logic in a separate scripting language and writing an interpreter for it was soon dropped (even by John Carmack who had implemented this concept) because of the overall inflexibility of an interpreted language,[3]"
On another side, there are a some games which used Lua for scripting:
http://en.wikipedia.org/wiki/Category:Lua-scripted_video_gam...