You are missing the point. Enterbrain didn't even thought about translating Rm2k3 to English. A FAN -the thread maker- requested to a staff of the English Publisher of RM (Degica) if they could publish it to the English Audience for the sake of LEGALITY and NOSTALGIA. Please read the thread. At least it shows that EB/Degica/However you'd like to see it is actually listening to their fans.
Owning rm2k3 means you can show off your rm2k3 game anywhere legally since you own it. You can also reuse whatever RTP assets it had in the newer makers since you own it, for whatever reason. Enterbrain has absolutely no reason or interest to bring it in English on the first place. The staff at Degica are RM fans that are acting as a voice for RM* fans to EB.