JOSM projection transformation error

I have loaded a shapefile into JOSM but get this message
"JOSM was unable to a strict mathematical transformation between ‘GCS_GDA_1994’ and WGS84.
Do you want to try a lenient method, which will perform a non-precise transformation (with location errors up to 1km)?
If so, do NOT upload such data to OSM!

I do not wish to upload the data but did want to view it using JOM but with error of up to a km it’s not worth even looking at really.

The data is claimed to be “They are GDA compliant and use the D_GDA_1994 Datum and Spheroid” and “GCS_GDA_1994 EPSG 8.2.6”

Can further projection libraries be downloaded to my JOSM (josm-macosx 9329) or would this be my opportunity to begin to use QGis, PostgreSQL, etc. or parse the shape file through another program - which?
I have GDAL: ogr2ogr installed too.

Edit: I think it would be preferable for me to ask Geoscience Australia what is the expected difference between these 2 projections for this file.

There were recetly a lot of projection related changes in JOSM. See Please try josm-latest (or wait some days until the next josm-tested version will be released) and if this does not help try the plugin proj4j. If this does not help you can create a ticket by clicking in josm on menu help → report bug and describe your problem.

Thanks, I will try next tested version.
The dev team has certainly done a lot of work on the projections recently.