Could Bukkit be released as a patch to the Minecraft server and therefore not violate DMCA? Basically take CraftBukkit.jar and the real MinecraftServer.jar and run some sort of binary 'diff' on it and then release the patch. Then end users get the patch run a binary type 'patch' command to create CraftBukkit.jar from their copy of MinecraftServer.jar. Of course diff and patch will not work since they are for text files, but you get the idea. Something could be created to generate a binary patch and then apply the patch.