If you mean Newton Script. I don't think you could do it directly on the Newton but needed a Mac (running OS9 and/or at least one with a serial port) to build your App before copying it over to the Newton. Other languages were possible but support was a bit thin (even then).
No, you need an old Mac running an old version of Mac OS. Possibly a copy of Codewarrior. You needed a Mac traditionally to do programming for Newton devices.