> Can you please elaborate here? I don't understand what you mean. > It is already the case that you can not relicense software under and incompatible license.

> Can you please elaborate here? I don't understand what you mean. > It is already the case that you can not relicense software under and incompatible license. Yes you can't, but currently in case for example Linux and ZFS and even BSD and ZFS. Programmers were able to use ZFS (note, it is Open Source but under CDDL) by implementing so called shim, that was providing API that ZFS was expecting. Ruling in favor of Oracle will make this illegal. Even within Open Source it could became a problem, for example FreeBSD implements Linux ABI (it's binary version of API) which allows it to run Linux binaries natively. Depending if the other side is hostile, this might no longer be allowed. Same thing with Wine. The law would prevent interoperability between all kinds of software, that's bad thing for all users, it's already difficult. > Let's say I write an amazing database. It's open source, and my license dictates that any modifications to the source code get contributed back. > Someone else clones the repo, guys everything except the APIs, and reimplements what's inside. They then release this under an incompatible, proprietary license. > Why is that ok? It seems like a clear violation of the intent of my copyright. And it's already what we see AWS doing, so this is obviously a lever that large companies are willing to pull. First of all, creating a good API is not trivial, but it is nothing compared to developing the actual product. If someone went the effort and create their own database from scratch that someone (especially if it is Amazon) would provide their own API, even today when it is legal to use someone else's. They would be concerned that having to follow other API would limit them, also it would make it easy to replace their product with Open Source alternative. You're saying that Amazon is already doing, I'm guessing you mean Aurora PostgreSQL and MySQL. In those instances they are using existing Open Source products and just replaced the storage layer with their proprietary. They can do this, because license permits them already. PostgreSQL license allows for commercial use without sharing code, MySQL is GPL but most likely they paid Oracle for the proprietary license. Ruling in Oracle's favor won't change anything there.