Your responsibility is to make sure they can get the code for a certain amount of time after you distributed it to them. So you can point to the origin source

Your responsibility is to make sure they can get the code for a certain amount of time after you distributed it to them. So you can point to the origin source if you feel confident that it will remain available for long enough, and if you know you can provide an alternative way to access it if that site goes down (so just keep a local copy, and if somebody tells you that the link is broken then you just share that copy).