I have to say, I like that Granite is actually a working (although a lot of stuff isn’t there and what’s there sometimes doesn’t work). I have a personal fork that I’ve been messing around with because it’s similar but at the same time very different to how we are doing it.
I think that due to progress made and plugin support it’s either going to come out with Spigot / Craftbukkit (if they can combat the DCMA), ourselves (if we are able to promptly get an API out and get the implementation going) and Granite (if they can expand their API and make themselves work well).
Granite suffers from a large amount of reflection and although it seems very well done from my pov, it’s going to be at least somewhat hard to update. Furthermore the reflection imposes at least a small speed penalty regardless.
SpongeAPI+Sponge: This is the main project, and it’s pretty good, however it suffers from not existing/having nothing to give people. Our dependency on not just FML but forge means that updates will be a bit slower than any system developed right on the server code. Note: This dependency is just in relation to the forge based implementation
Glowstone+SpongeAPI: This pairing is cool, but suffers from Glowstone’s continued lack of a full implementation of vanilla Minecraft’s functionality. Hopefully the flood of programmers that sponge brings will fix this limitation and it will update in a way similar to Forge and FML, changing only the implementation of the protocol and adding support for new features.
Obviously any Bukkit based system has the (very small) risk of Mojang’s ownership of the API. And anything based on Craftbukkit has the DCMA takedown to worry about.
Rainbow seems sketchy to say the least. It’s got a jar out and some starting (poorly coded/crap) plugins. But I couldn’t find any source at all which isn’t a pleasant thing to think about. I have also discovered that they bundle the vanilla Minecraft server jar with their download. Which, after all that has happened, is not smart at the least. As for their code, it’s not great. They don’t even seem to have their act together as much as the Bukkit team did. I will update this with more details once I’ve played with it more.
To wrap up the largish projects I would say that Husk has a good website, a good idea and possibly offers real competition to Sponge, but is being hush hush while they hammer out the API and implementation. Possibly waiting for the competition to become more clear giving them a direction to follow with their API. I’m interested in the outcomes here.
Note: If you want another platform appraised, just send me a PM.
Update 1: Updated Sponge information to mention Glowstone and added more information to Rainbow.
Update 2: Found Glowstone implementation beginning and added separation to Sponge vs. Glowstone implementation.