Yeah I thought you'd ask this. Basically they'll never do this, just because their attitude is "fuck you I'm a bank".

Beyond this, there's a big difference between source code and having a working system.

For very long running systems their state depends very heavily on how they were maintained, little bits of informal design decisions that get components working together, and the order stuff was loaded in, and what other services were up and running when you booted up.

None of this magic is captured by source code, and it can make even setting up a replacement server, even as part of the same infrastructure really hard.

Of course banks are moving to more modern dev methods that encourages turnkey deployment, but the fact that they still rely on a bunch of COBOL code tells you there's a lot of very old system running in "do not touch" mode