A lot of older cards were not like this (pre-DP Deoxys, the Unown family, etc).
But the trend in DP-on appears to be that the additional text (everything except for the level, at least) is considered part of the card name. So you can run 4 of each. There is no official word on the new Deoxys and Castforms, but I have little reason to doubt that this is the case.