Ettiquette For Restarting Abandoned Open Source Projects?

nicsterrr asks: "What does one do when a promising open source project stops dead with no word from the developer(s)? I have been considering contributing to a certain sorceforge hosted project over the past few months, but unfortunately all development seems to have stopped and the main developer has vanished (from the internet at least). I understand that the GPL states that GPL source code can be used in derived work if the licence is unchanged, but I am hesitant just to 'hijack' the work done by (it seems) just one person, without first having an understanding of what his thoughts are first. In addition, there are almost no supporting comments in the code, and no separate developer documentation. What would you do in this situation if you were interested in furthering the undocumented, unfinished, and currently abandoned work (which at first glance seems to have potential) of someone else, and your attempts to contact them have been in vain?"