That's interesting. Where is Lisp used at Google? I vaguely recall reading long ago that Google had some kind of policy against using Lisp or Smalltalk for projects, but I can't find the article I am thinking of [1].
[1] I'm not 100% sure, but it was probably some kind of article about "programming languages used by Google in production." I recall it talking about how C and Python were approved, as well as Java (~"because there are a lot of good programmers who write Java"). Lisp and Smalltalk were explicitly banned, mainly because engineers so frequently proposed using them because of their appeal, despite the supportability issues w.r.t. skillsets.
That's close, but I think it's reflection of the same policy, not the same article. The article I remember talked about more languages that just Lisp, Smalltalk, and Java. It was overall down on Java, but had positive things to say about some Java programmers.
Pharo would be the practical one, Squeak the less industrial one. Lots of stuff has been implemented with both, enough that you could run a consultancy and build applications for people.
You'd need to be a bit of a Smalltalk nerd though, and be prepared to do most of the work yourself since there aren't that many smalltalkers to recruit from. You'd also be in competition for developers with companies building software for insurance or ERP, and many smalltalkers spent relatively much time in academia so that could affect salary expectations.
Mediagenix's "What's On" ( https://www.mediagenix.tv/whats-on/ ) is written in Small-talk. The main reason is the company's ancestry had strong academic roots, but it worked for them. It's not Open Source, but since there aren't that many successful commercial Small-talk products in the wild I thought I'd mention.
Absolute mountains. Consider: Ruby is Smalltalk with alternative syntax and core library.
I'm only being a little bit flippant here; the only core language feature in ST that Ruby is missing is thisContext, and most of the things that end developers do with thisContext (continuations, exceptions, and the debugger) are natively supported by the standard library.
[1] I'm not 100% sure, but it was probably some kind of article about "programming languages used by Google in production." I recall it talking about how C and Python were approved, as well as Java (~"because there are a lot of good programmers who write Java"). Lisp and Smalltalk were explicitly banned, mainly because engineers so frequently proposed using them because of their appeal, despite the supportability issues w.r.t. skillsets.