Jukka Rahkonen - 2013-03-28

The OpenJUMP WFS-plugin should be marked as unmaintained and non-operational. It just does not work anymore and OJ developers do not have the knowledge to repair it.

Kosmo GIS has a pretty good WFS support and before summer there should be a new 2.1 version available with WFS-T. I do not know how far apart OpenJUMP and Kosmo are nowadays and if it could be possible to re-use the WFS-T plugin.
As a workaround you can use GDAL and ogr2ogr utility for reading data from WFS server and converting those as shapefile for OpenJUMP.
http://www.gdal.org/ogr/drv_wfs.html