Well, I was one of several who were supposedly going to help update to 1.7 (before AP switched to MF2); before that it was all AP. There was no formal declaration of rights, or statement of a license for the code -- it was more of an informal agreement through which I was given access to the source code. I don't remember exactly, but I think Mangoose and Janivere (under the name Eruraion) were involved, though it was a long time ago so its fuzzy -- we didn't really accomplish anything. I'm pretty sure Mangoose doesn't have signed document, or any particular "rights," either but has made versions on his own (with significant changes) since then. The only one I know to be officially charged with continuing the project was Nofole (though I was marginally involved) who was working on a MF1.5, which changed the mod beyond recognition but was never finished -- unless you count MF2 being given to Sirse. I'm not trying to "steal" the mod, I'd just like to make it more readily available and keep the idea alive -- preferably as close to AP's original as possible. Unfortunately, I don't think AP is coming back.
Having said that, the further you go in version from 1.6.4 the less some things make sense (e.g., repair hammers in a world full of mending books). Backporting the newer the mods would be preferable, but downloading the needed files for Forge development to work doesn't seem to be possible anymore. Perhaps a brand new 1.6.4 server with Minefantasy and Climatic Biomes would be nice? This mod improved the game more than every vanilla update since I started playing back in 1.4, or any other mod I know of.
But having said all that, I doubt it will happen -- I'm largely retiring from modding and need to put the time it would take into other things. I'd just love to have it back, and be able to play it on a world with more sensible geography.