When attempting to run the latest builds of Forge (200 to 230) on my headless server (no window managers of any kind), the server fails to start.
Console output: http://pastie.org/private/q9clitpw0ojo0vkczmw5ag
No Forge*.log or ModLoader.txt is created, as the server fails before any such things happen. No patcher or launcher is used. Installation of Forge is in minecraft_server.jar (not the client!) and contains ONLY the builds mentioned above (minecraftforge-universal-4.0.0.230.zip, for example), no ModLoader or ModLoaderMP.
From what I can gather, the issue is specifically limited to the lack of an installed window manager; whether or not it is running seems irrelevant (with X11 installed I can start the server even without Xorg running). The same jar works on both Windows and Slackware Linux so long as a window manager is installed.
I'm fairly confident that the problem is the lack of a null check in Downloader.java, after it fails to instantiate an instance of the JOptionPane due to a lack of any installed libraries with which to create said pane.