Glest Multiplayer Support
Its seems martinho & co have been busy over at www.glest.org and have released an alpha build of version 3.
Whereas spring built multiplayer support from the ground up followed by skirmish AI support, the glest engine went the opposite way around. Their current multiplayer support is a little rough at the edges compared to spring but its a great step forward. The main downside is that to start a game you have to mess around with IPs.