Party A (not necessarily a company) writes software. The software can be open source or closed source, I'm not sure it matters for the sake of this argument. Party A has license terms on their software that restricts copying or at least requires attribution.
Company B also writes software. Company B's software is closed source and commercial. Assume that they use strong enough obfuscation on their software before releasing to their end users such that the released product's compiled code is unintelligible and can't be reverse engineered back to the source code.
Someone accuses Company B of using Party A's source code in their software without properly following the license terms. This could be outright copying and use of proprietary code from party A, improper attribution or some other breach of the license terms while using A's code.
Company B has a right to keep their source code private from the general public. I understand that this doesn’t mean they have a right to keep it secret in legal proceedings.
Given that the source code is kept secret from the general public, how can a legal challenge against company B ever be successfully mounted for this accusation?
I would assume that if the evidence was strong enough then a court would order company B to allow its code to be reviewed by a 3rd party appointed by the court.
If that assumption is correct then the question becomes what level of evidence is considered strong enough?