There is a simple solution to this. When you publish open source software, make sure that in your license it says that Goldman Sachs is not allowed to use this code for any purpose whatsoever.
If you don't want to deliberately confuse people, you would say "the source code is available" or something like that, because most people take open source to mean this:
I wonder if they'd care. Sounds like they don't particularly care about the licenses on the open source code they use, and I doubt you'd find out that they're violating your license.
http://opensource.org/osd-annotated