I don't think you can.

Lion uses HFS+, and Snow Leopard deprecated HFS Standard by removing write support (the reason for it being locked).

System 6 doesn't understand HFS+ either (read or write), unfortunately.

I think there's something called MacFUSE or something like that which offers experimental write support for HFS Standard under 10.6 and up, so you could try that.

Beyond that, I don't think there's much you can do.

Sorry,

c