I guess what I'm asking is if Oberon-0 is a subset of Oberon-7, which oberonc seems to implement. Do you think it is possible to implement Oberon-0 in itself ?
Oberon-0 is too limited to easily bootstrap itself. I wrote oberonc first in Java and then I rewrote it in Oberon-07 for the final bootstrap step.
Oberon-0 is a toy subset of the full Oberon-07 language.
Yes, you can write small Oberon-0 programs and compile them with an Oberon-07 compiler, but it is simpler to just use the Oberon-0 compiler from the repo above.
I guess what I'm asking is if Oberon-0 is a subset of Oberon-7, which oberonc seems to implement. Do you think it is possible to implement Oberon-0 in itself ?