Is that a Plugin that does Teams and such? Because for that I don't even need Forge, since it is a recent vanilla Feature.
And even if it wouldnt be vanilla, it is easyly doable with Forge.
Factions is an interesting concept, it works based on chunks. There are teams, teams get an amount of chunks that they can claim, that amount increases with the more people in the team and how long alive they have been. If their allowed chunks drops below their chunk count (like due to players dying or rank going down or so) then some of their chunks can be claimed (only if not surrounded by other claimed chunks). A claimed chunk cannot have blocks broken or placed by opposing teams but (I think) can still interact with things like chests so you have to set up defenses using pressure plates, tnt, lava, etc... Those tend to have teams build TNT cannons to launch tnt to a claimed area to blast holes into walls so they can invade and raid their chests and more. Interesting concept, though I like forcefields better, less magical than magical claimed unbreakable/unplaceable chunks. Used to play it way back in the day pre-Forge. That and Towny were big ones on servers depending on anarchy or not and so form.
And yes, everything done in a bukkit plugin can be done in Forge in one way or another.