But to answer your question: Mike Bloomberg's autobiography talks about this. When they started in the 80's there wasn't as much great off-the-shelf software as there is today.

Their customers were (and always have been) insanely demanding when it comes to reliability and speed. The last thing Mike wanted to do was be caught sheepishly explaining to the CIO of Merrill Lynch, "Well, gee, our Oracle database has this bug they can't fix for the next two weeks..." or even "...this optimization they can't make for the next six months"

This is a company that invented its own layer-2 network protocols 35 years ago just to squeeze every last drop of performance and reliability out of the hardware. Of course they wrote their own database (actually two -- there was a comdb 1 of of course, too)

To directly answer your question: go look at where 'replication' was on rdbms 14 years ago. PostgreSQL? MySQL?

They probably open sourced the database, and would do more -- to dispel the above notion, and therefore to attract more qualified recruits.

Financial services companies, and technology suppliers around them, have came up much of the 'modern day' tech, some times decade(s), before google's and facebook's of the world

  -- have had NoSQL with stored procs(eg Goldman S, early to mid 90s ),   
  -- in-house grown programming lang (APL+ based in Morgan Stanley) emphasizing vector-based operations
  -- Smart contracts 
    https://www.lexifi.com/product/technology/contract-description-language
  (where a contract is represented as algorithm specified in a domain specific language) 
    ).  This was way before etherium, started, I believe, in Credit Swiss (but not sure)

   -- one of the fastest time series database (kdb+)
   -- Data science and machine learning (modeling risk and valuations)

>> We had several goals in mind. One was being wire-format compatible with an older internal product to allow developers to migrate applications easier. Another was to have a database that could be updated anywhere and stay in sync everywhere. The first goal could only be satisfied in-house. The second was either in its infancy for open source products, or available at high cost from commercial sources.

It's not that uncommon especially if you've been around a long time.

Edit: As someone else points out, they were doing cloud computing before the internet existed.

I remember when we didn't even have comdb2.

https://en.wikipedia.org/wiki/NewSQL

I can't think of any solid distributed RDBMS that would have been around in 2004. Does anyone with more knowledge have any idea (open or not)?