It's a Naomi game. One of the primary reasons to use a system like Naomi (or ST-V, for which Radiant Silvergun was released) is for compatibility with the console version of the hardware. AFAIK, almost all Naomi games have a DC port, and some are actually ports from Dreamcast IIRC.
It is definitely a 2-player blastfest; Treasure would not have it any other way! After Radiant's inspiring awe in the plethora of game options-(dogs, etc...) They will have to put some of the same effort if not more in Ikaruga for Dreamcast.
This is how it goes:Ikaruga has been anounced for the PS2 too,so i think their just bringin it out for the DC fans that want it (in a limited number of games printed),and the PS2 Version is supposed to bring in the cash..like Sega did it with Space Channel 5 Vol. 2...
It will have a 2 Player mode.Thae arcade has one,the home version has one