Cool! I've installed it and it seems to work plausibly, though it's an old enough version that its "export URL" function is no longer compatible with the site. And the site has more features.
The validation question is interesting to me because I'd like to do things that go beyond just academic exercises, so I'd like to know how much confidence to have that the physical devices behave as modeled.
www.falstad.com/circuit-java/