This is a simple BungeeCord chat plugin, tested with the most recent BungeeCord and Minecraft 1.8.7. It adds the '/g [msg]' command to broadcast a chat message to all players regardless of which server they're on in the network.
There are no permissions, anyone can use it. It's a simple global chat for my server and I thought I'd share in case anyone else wanted it.
Source code available at https://github.com/aRottenKomquat/GlobalChat