Fun fact- Country with highest terminal density per person? Vatican. Hail Mamon
"The ui is hard to learn" is a selling feature not a problem. It's like sabre or amadeus: it helps the industry keep out time wasters and maximises the agents sense of skill and value.
The socialised effect of "trade in Bloomberg or get a worse deal" probably makes the alternatives very niche.
If something like the LME had developed a terminal I could see it having the same value to it's community, or the bank settlement systems. Something used by most of your cohort, easier to stay inside it.
It's contract enforced API access. Illegal scrapers risk being excluded. If you pay the fees you get the spec apparently.
What, not enough white space, animations, and shitty, obscure menus for you? Or maybe they need Material 69 or Liquid Glass?
I would have thought if they would have move anywhere, it would have been to Linux or maybe even a *BSD to avoid the GPL.