There was a separate per game Konami ID I remember. So you need your PSN, Konami ID, and one other one to just play. Each of those had different password requirements (like must contain 5 upper case letters and at least 2 numbers). It was a mess.
Also, if you played the MGS4 beta I *think* that the Konami ID from the beta couldn't be reused for the actual game. It was either that or I completely forgot my credentials and there was no way to recover those deets for your konami ID.
And they also sold DLC maps only through their website. It was super duper shitty.
I think they eventually released either a MP demo or just the MP as its own thing on the PSN store but I don't think they ever put the maps on the PSN store.
The whole thing reeked of Konami wanting every single penny for itself while ignoring the fact that if they had reduced the barrier to accessing this shit then they would've likely made a shitton more money instead of wondering why their fantastic business plan failed to gain any traction.
I guess i'm glad it failed because it probably stopped other third party publishers from trying some shitty stunt like that themselves.