Here’s an interview he gives with Newsarama about it and his current arc on JLA: Classified. This is another Newsarama piece that has more info about the characters and artists. Finally, here is a page from a nice Morrison interview from PopImage in which he talks about the structure of the project (although it appears to have changed some since then).
The basic rundown – it’s 30 issues total. Two bookends plus 28 issues broken into seven four-issue miniseries, each featuring a separate character. The idea is that each of the minis can be read separately to tell a satisfying story but that they can be combined into an even greater whole. Contrary to Morrison’s belief, this has been tried with some regularity over the years (e.g., the Superman relaunch of about five years ago, not to mention CrossGen’s entire output), but it’s never been a total success. Personally, since I’m planning to buy them all anyway, it’s not much skin off my nose whether he succeeds or not in his modular approach.
The original Seven Soldiers of Victory (aka The Law’s Legionnaires) were the feature of DC’s Golden Age Leading Comics. The history is complicated, but back then DC was actually two companies, National and All-American. National published books featuring Superman, Batman, Spectre, Starman and others, AA had Green Lantern, Flash, Wonder Woman, Hawkman, Atom, etc. AA published All-Star Comics featuring the Justice Society of America. The JSA was made up of two characters from each of National and AA’s anthology titled, the idea being that fans of, say, Dr. Fate and Spectre from More-Fun Comics would follow them to All-Star, be intrigued by Starman (Adventure Comics), Hawkman (Flash Comics), or Johnny Thunder (All-American Comics), and then pick up the monthly anthologies featuring those characters as well. National’s Action Comics and Detective Comics didn’t contribute characters because they had Superman and Batman and didn’t need the bump.
All-Star was a huge hit, and the National side wanted a similar project, so it created Leading Comics. Leading starred the Seven Soldiers of Victory, which included Green Arrow and Speedy (from More-Fun), the Shining Knight (Adventure), Vigilante (Action), the Star-Spangled Kid and Stripsey (Star-Spangled Comics), and the Crimson Avenger and Wing (Detective). Yes, that’s eight members, but Wing was considered honorary and didn’t count.