Forge's nearest cousin in look and play looks to be Unreal Tournament, but rather than three-barreled rocket launchers and dual pistols it's fireballs, demon-summoning, and oldie-world bows and arrows. Another difference is that weapons aren't littered about the level, rather the character you select has in-built abilities/weapons with which it can attack - Pyromancer's are loaded up to the cockles wall of fire spells and flame tornadoes, whilst the Assassin can curse their enemies (essentially fitting them with a magical timebomb). So, it's a class-based system where the abilities of your class are with you from the moment you spawn.
To get a better idea of the project here's an explanatory video from the Kickstarter page:
And here's a bit of the game in action:
Forge is planned to launch with a fairly low entry price (around $15) with DLC packs of new characters flowing thick and fast. A similar model to compare would be LoL or Tribes: Ascend.
The game's apparently in a late stage of development and the $300,000 Dark Vale are seeking in funding is get it out the door. They're almost a sixth of the way there with 25 days to go. Though, they do say that " One way or another, FORGE will be built and released." So,even if they weren't to get the funding, this is a game that's going to ship. This is spit and polish/publicity & community gathering.
For even more details, here's a lengthy play session from Total Biscuit: