On Debian/Ubuntu dash is probably the closest thing. Other distributions may also have ash.
https://en.wikipedia.org/wiki/Almquist_shell
Yes, tcsh(1) is also available on most distributions. Although the versions might differ a little.
It is. As far as I know 'our' /bin/sh is also based on the original Almquist Shell. There may be some small implementation differences but they should all be compatible with each other. The differences certainly aren't as big as the differences with bash for example.Isn't that basically the same as the FreeBSD shell?
Not much indeed. But I have noticed some slight differences on various different Linux distributions compared to FreeBSD's tcsh(1). It's good to be aware of itYou almost make it sound like it undergoes a lot of changes ;-)