Actually i heard that there's a workaround for you US ppl to download things from the JP online store - Google it if you want it i can't remember where i found it sorry but it worked something like this:
Set up a new account with certain privelages (ps3 isn't out in the UK yet so i don't know how it works and couldn't remember what type of account you needed to make sorry)
Set up this account as being japanese somehow, again i don't remember
You only need a japanese credit card for purchases over $14 or something like that and the trick was to buy multiple sets of playstation store points in small quantities or something, either way there is a trick to obtain enough points to download these things - if it's free it might not even need that.
Sorry if that was totally useless but if someone looks it up and gets it to work that'd be awsome.
Actually now that i think of it i found the link to the original article somewhere on digg.com but you'll have to be very creative with your searches to find it - It didn't mention anything about DMC4, just a trick for the playstation store.
Sorry for double post, i just did some searching on digg and found the original article:
http://www.gamersreports.com/news/4667/tekken-5-dr-in-ps3-store-in-japan--gr-usa-workaround/
I hope this is of some use to someone if DMC4 is available to download and works