The license of the previous code didn't magically become the GPL altogether, instead it by default became un-distributable. They were required to (a) stop distribution of the existing code since it at best had no clear license, and (b) if they wanted, going forward remedy the license by clearly making it GPL or doing the rewrite of the dependency. Or even reach out to the library author and ask for an LGPL or other alternative - there is sometimes (often?) some flexibility there.

The built-in conflict resolution in the GPL is no-distribution.

Depends who had rights to the proprietary code. If it was someone else's (for example, if the internal version had used both GPLed code and some proprietary third-party library), open sourcing the whole thing just might not be possible.

> Quickly removing the code doesn't change the previously released versions' license.

But would $BIG_CORP publish source on request for a proprietary product just because they built one version with a GPL library by mistake and later fixed it? Has this been successful, ever?

Isn't this how OpenWRT got started?

Depends on the composition of CORP. If it is comprised of developers with strong respect for OSS or FS community they might not stand for non-disclosure. OTOH, plenty of orgs would be mainly folks without a strong opinion either way and would just follow executive direction.

> ... or just go with it and have it be open source?

They didn't have the legal right to do so.

How is that? The company added code to a GPL project, that means it is a derivative work and also comes with software freedoms, or at least that's how the story reads to me since there is no mention of other claims or parties to the mix. That means the company owns the copyright to the added code and is free to comply with the contract (license).

Company A writes library with commercial license.

Company B uses that library and a GPL library in a product. They distribute the product.

Company B has no right to relive se Company A’s commercially licensed library under the GPL. Hence, stop distribution and replace GPL library.

See:

> ... since there is no mention of other claims or parties to the mix [like company A]. That means the company [B] owns the copyright to the added code and is free to comply with the contract (license).

I'm also not sure whether the confidentiality clause would weigh heavier than a 'must provide source on request' clause, perhaps it could be resolved by not distributing the part that's covered by the confidentiality clause since another standalone library is clearly not a derivative work of the GPL-licensed library. Then only B has to distribute what they made for everyone's benefit.

It does hopefully prevent any of your customers from ever asking for it.