Essentially. Police or anyone could report an account for illegal activity which is against ToS for all three of the services. From there the service would need to be able to substantiate the claim and then shut down the account. I've seen a few cases of proton accounts getting shut down. Proton can't read emails but they can read headers and if you've posted illegal activity in public using your proton email address or if law enforcement/ someone reports you for using proton for illegal activity then proton will be able to review headers to determine if you're violating ToS. Like a few years ago i think someone was using proton for ransomware, and proton was able to match the headers with emails that had been posted in public, and acct got shut down.
Unfortunately can't find that specific case but that was one example I've seen
If you haven't already, check out https://choosealicense.com/licenses/ . This gives a broad overview of the common open source licenses. And if you're just starting out, one of the first things you'll want to learn is that the licenses fall into either a permissive or copyleft category. You'll want to make sure you understand the difference between those broad categories.
Shortly, permissive have less to no strings attached to use their code, and copyleft requires you to retain the same licensing terms meaning if you publish under GPLv3 then someone using/ modifying your code needs to also publish under GPLv3. Copyleft licenses ensure that open source code stays open source.