Long story short, it's entirely different as a focus. HC is designed around customs, and also designed to compliment other sites rather than avoid competition. ForgeHub is ForgeHub, they're a place for maps. Here, we have a board for maps only to accent our focus on customs. We encourage our members to be a part of as many communities in the Haloverse as possible; we actually will be reaching out and showcasing other community's content. It's like "go be a part of wherever you want, but here will be around to host customs, and if you're a big customs guy then maybe you should stick around". We are in no way competing with ForgeHub.
You may not know this, but I was actually the founder of the ForgeHub Tester's Guild and then the subsequent rework, the TRC Guild. I had intended on it becoming a "focus" of ForgeHub, to center around it, but it ended up going the other direction, towards a map depository resource. I think you can easily see the connections between this website and the design for the TRC, but the sites are very very different.