Here's a post on the bukkit forums about the meeting the people from bukkit.org had with Mojang about mod support:

On Wednesday morning, as I'm sure most of you already know, the Bukkit team had a meeting with Mojang Specifications regarding their popular game, Minecraft. Going into the meeting, we were hoping to tackle the licensing issue right out of the door. Unfortunately, due to some people being unable to make it, it turned out to be a different type of meeting than we had intended.

With only the developers of Minecraft able to attend, the meeting quickly turned into a technical discussion about what ideas we all had for Minecraft, how modding should work and so on. As we learned a lot from this meeting, we felt we should share some of the points with you. However, please understand that absolutely nothing said in the meeting is set in stone or final and can change at any time.

So, here's what we learned:

• Modding support will likely start as server-side only at first, then later is hoping to expand to the client-side
  
• Single player is most likely going to be changed to run through a local server (this is also to enable modding)
  
• They are hoping to make texture modification easier, without having to modify the client
  
• They like what we're doing but need to provide us with a better alternative to the way we're doing it

Some ideas they're considering:

• Generic gui support
  
• Server -> client communication to allow popping up an interface, etc
  
• Being able to tell clients to follow different rules, like physics
  
• Giving modders the ability to (make signs) show text

While we did not have time to address our licensing issues, we believe we can honestly say that this meeting was just the beginning of a long-term relationship with Mojang Specifications. Nonetheless, we're hoping to contact Mojang Specifications specifically about our licensing issues soon.

EvilSeph @ Bukkit.org

Guess bukkit might not be released as "soon" as we were hoping.. But it's at least going in a good direction

Heh, Still sorting out their issues with that?

Bukkit mod in singleplayer? Oooh, that'd be fun! (If I read that correctly.)