If you're a teacher and doing this for educational reasons, you can also make up your own boards if you have an appropriately-size map of Europe you don't mind altering. Just laminate it, draw borders labels and borders in the appropriate places, and find or make something to use for fleets, armies, and to identify each player's territories. If you have to stop the game, just write down where all the pieces are, take them off the board, and roll it up till next time.
If you do this, make sure the students refer to places by their proper names, not necessarily the Diplomacy ones (Istanbul, Izmir, Netherlands, etc). The disadvantage is that you don't have a computer to help you with all your moves and to prevent cheating, but the advantage is that you have students interacting with each other personally and learning European geography from a real, high-quality map.
Also, you might be able to get the latest source from the developer, Kestas (kestasjk), so if your school has accommodating tech people you'd be able to set up a private server just for class use.