Greenfoot devs said they won't?
Greenfoot devs didn't say the will; which means they won't :D
No one interested in doing something like this? :/
Who were you thinking of using to host the server?
The reason there's no plans to implement this at the moment comes down to the same reason there's no 3D support in Greenfoot - it would be a huge step up in complication (all sorts of issues crop up with such multi-player games, indeed many of the big games often have synchronisation bugs because of these issues) and considering Greenfoot is aimed at making it easy for beginners to get started making cool games, this wouldn't really be directly in line with what Greenfoot aims to achieve.
However, if you do choose to go ahead and setup a server and implement this, bear in mind that you still have a bunch of issues to get around - most obviously the fact that sandboxed applets can only communicate with the same server they're hosted on. Or in other words, if you set up such a server and provided an API, it would never work on the gallery, you'd always have to download the scenario first.
So while this sounds cool in principle, in practice you forfeit the distribution platform (the gallery) as well as the novice appeal...
It should also be noted that you can manipulate the user storage mechanism to provide such multiplayer activity if you want to - it won't be blisteringly fast at all, but will work with the gallery fine. With that in mind, perhaps an alternative project could be to develop a more user friendly API that provides real-time like method calls but uses the userdata mechanism underneath? Just an idea.
@mjrb4, what do you mean by manipulate the user storage mechanism? Do you mean using UserInfo like I did with my Battleship game, or making something new like the UserInfo class with same stuff underneath that just has a different API - which case wouldn't be different besides friendliness in terms of being aimed at multiplayer?
I would be in support of using a game server, that'd be fun :D
Are you going to make another mod for greenfoot to access the server, will it be another addition to GF3D, or will you have tutorials on how to use it?
Also, would you support the server (Doubt it), will you have ads to help support it (on the server or somewhere else) or will we all pitch in if we wanted to? (trust issues arise obviously, but it is the internet)
I might write something to use UserInfo to multiplayer.
Check this out:
http://www.greenfoot.org/scenarios/10597
Works for onsite user 2-player games (turn-based or similar style)