'MS let a major global bank have access to the Windows 2000 source code to aid them in coding some low level bespoke software.' Examples of this are comparativ

'MS let a major global bank have access to the Windows 2000 source code to aid them in coding some low level bespoke software.' Examples of this are comparatively well known but it seems to me it's really not relevant here. In those instances it's extremely unlikely that said institutions would have access to even the majority of the source code let alone all of it. All they need are API hooks and or various security code that's relevant for their purposes, etc. If I were the Microsoft person responsible for interfacing with these banks, I'd do what I've done with unrelated stuff, which is to tell them just sufficient to do the job (that's to say only on a need-to-know basis).