Close friend in college managed to do a lot of Snobol4; I got the impression that it was a language based around string transformations, like regex everywhere.

Mathematica is essentially a transformation engine like that.. A standard Lisp unification engine, initially.

And didn't Snobol lead to some language that's embedded in large healthcare management systems?

Indeed the primary usage was text and string manipulation; it had a huge following in the 70s and 80s in the humanities. However, like with most languages, all the bases are covered for complex functions, mathematics, etc; it just never got as much traction in those spaces. Far as I know it was the first language to use associative-arrays, it also supports backtracking (like prolog), and meta-programming (code generation during runtime), map functions, lambda like functions, etc. It really had it all!

https://thedailywtf.com/articles/a_case_of_the_mumps makes unflattering comparisons to both FORTRAN and SNOBOL, but it sounds like its own special hell.

MUMPS - that was it. The Sendmail-config of the healthcare industry.

Are there any free implementations of Snobol4 available? Every couple of years I search for them again and I only find broken links...

(Btw, Icon - Snobol4's successor - was my favorite language for several years. When I tried to learn Snobol4 by myself in the university I couldn't understand its semantics, but the book "The Icon Programming Language" was superbly written and it explained generators and backtracking very well).