LaunchGUI for Minecraft 1.9/1.8.9 creates a menu with a single button and up to 10 lines of text right before the main menu. It will disable itself once the button is pressed. A utility for modpack creators that creates a GUI when the player initially launches the pack.
Download link: LaunchGUI for Minecraft 1.9/1.8.9
Read more: Minecraft 1.9 Mod