[PostOnce]

Burroughs MCP impresses me with its lifespan (which is ongoing)

Initial release 1961; 59 years ago

Latest release 19.0[1] / June 2019

I wonder who uses it today and for what?

[smortaz]

Definitely. The OS, HW and Extended Algol had some nice features that were ahead of their time. I haven’t kept up, but their mainframes were very popular with banks etc.