I think the Dredgeworks mod expects the name of the item used in the code to match the name of the actual inserter used in the code, because that's how Factorio decided to name things. I don't name things the same way so if I had to guess that's why it expects an item with the name "PlayerLauncher". I call it "PlayerLauncherItem" just to help me keep things straight in my mind. You'll probably have to ask the Dredgeworks guy to adjust his code to be more flexible. I could adjust the way my things are named but I'm sure other people also don't use Factorio's naming choices