Since you probably are not part of the tech world or the security world, I will break this down for you best I can. In the 1990's, the government tried to sue a group of hackers who published software for the sole purpose of hacking, then companies started to do it as well. The defendant in the first case (I cannot remember his name, I am exhausted right now) appealed all the way to the supreme court. His argument was that source code was a form of protected speech the same way art and literature are, because when you write source code, it reflects the authors creativity and is a reflection of themselves. Which is true, every coder has a unique style, and they approach problems if different ways and the software they write is a reflection of what the coder desires.
Supreme Court ruled, and has since upheld in every case that source code is protected speech
And the makers of the OS release it as source code with automated build for ease of use, however it is highly advisable to build Graphene yourself, and that is what the documentation says.
What the courts did rule however is the user is liable for anything they may do with that software. Take for instance the company I work for, Setec Security Research Labs. We have software that is designed to take down entire infrastructure such as satellite disruption tools, distributed denial of service attacks (DDOS) to knock people of the web, etc. While we build these tools for testing, which is perfectly legit, but if you went and download the open source tools we have and say your boss was being a huge cornhole and decided to use the tools against him, you are liable for your own actions, not me. Just becuase I gave you the gun, doesnt mean its my fualt if you killed someone with it.
Its why groups like cellbrite and NSO group can get away with creating spyware that gets whistleblowers, dissidents, journalist, etc killed. While I am against any company that sells those kinds of tools (and we actively release free tools to prevent those kinds of malware and intrusion devices, our main open source tools), they are completely legal(ish). Our own government uses tools from Cellbrite all the time, like the Iphone cracker used against the San Bernardino shooter (they have legit uses). But governments like Russia use them to kill anyone who speaks out against the government. Its same with the criminal groups (who now spends millions upon millions of dollars, creating software and infrastructure to run scams, exploits, spyware and such).
So GrapheneOS is 100% right.
(sorry if its sloppy, like I said im tired af. I was up all night writing code)