Sure, but in America, anybody can sue anybody for anything. Your lawyers are of course right that having a clause in a software license disclaiming all liabili

Sure, but in America, anybody can sue anybody for anything. Your lawyers are of course right that having a clause in a software license disclaiming all liability for its use could be helpful in your defense -- but it's not an ironclad guarantee that you will not be sued or even found liable for your contributions in the event that it causes some kind of catastrophe. If this is a major concern for you, you should probably avoid contributing to FOSS altogether. However, if you don't own the software and don't distribute the software and don't have any other kind of relationship with the users of the software, it's likely going to require the plaintiff to demonstrate particularly egregious conduct on your part in order for a court to find that you have some liability for damages arising from the use of the software. But YMMV.