Banks and fintech often view their in-house tech as competitive advantages, and they usually don't care a whit about building cred in dev communities (a common reason why projects are OSS in the first place, to drive recruitment or promote a complimentary platform).
A good outcome isn't impossible, but it might be unprecedented
We all know the history of acquihires. Key tech and products inevitably are swallowed, never seen outside again.
Besides that, datomic really is a great solution for banks and fintech....are other firms like that going to buy from another bank, maybe a competitor?
If you asked me that 15 years ago, I'd say "no". In hindsight, it sort of makes sense given their objective of increasing time spent online and the quality of the experience.
The proposition here is that nubank will be the first bank to successfully turn into a software vendor. Maybe my worries will be nothing in 10 years, but no one can say its an obvious outcome.
This is great for nubank, but how is this supposed to work for other users of Clojure and Datomic? Who is really going to be interested in building on top of tech owned by a (new, unknown, regional) bank?
Someone said that this is just like Amazon (who would build on top of tech from a bookstore??), but I hope it's obvious the two situations are very different.
I expect that I'll have to be looking for a new job in a year's time :-(
A good outcome isn't impossible, but it might be unprecedented