using AI you can get it to like 80% completion but things like boss scripts are really hard to do. it really is just like 10% core, you have maps, monsters spawn in but you have to enable all the quests manually (or with ai), a ton of things like portal locations, runes, harvestables, the minigames, all the usable/consumable items/etc. the source includes most of what you need but unfortunately bosses and like one of fritto's minigames are either impossible or really hard to implement with the available source. might be other stuff that wasn't fully implemented by time i stopped working on my copy since I was just seeing how far I could go.
i basically just modded mine to enable all the anime collab stuff, mess around and level a kanna up a bit with regular xp rates (also have to change those LOL)
(also someone else made a 265.3 launcher with some server scripts, start from there.)