> Guess which one caught on for real world usage and which ones mainly stayed in academia. Exactly.
Selling Oberon compilers for embedded systems since the late 90's
http://www.astrobe.com/default.htm
z/OS is coded in a mix of Modula-2, PL/I and Assembly. Newer parts of the system are nowadays written in C++.
The problem with any systems programming language is that it needs to be forced into developers by an OS vendor, otherwise very few will use it as such.
This is sadly what happened with those languages.