Dunno why they're doing it like this, I would have gladly paid for this. Happy to see it's releasing so soon.
Also don't know why it's so difficult for them to just say it's Forge and Custom Games if that's the case. Both announcements now make it trivial whether they mean Forge and Customs, or just Forge with 16 other players.
Also, Halo 3 had a content browser available from Bungie.net 9 years ago. The fact that 343 is still incapable of meeting even that standard this long after Halo 5's release is incredibly disappointing. I remember when I could be part of a Forge community, check out posts on a forum with pictures and descriptions if a map, and click a link in my web browser that would direct me to a download page for that map/gametype, which would queue up the download on my console the next time I booted up Halo 3. That was incredible.