I had created a wiki page regarding webGRASS and also some demo videos because its still under development.
webGRASS does not use any WPS or WMS services. it will work just like a desktop GRASS and users only need to carry data no install and configure
nviz is not supported but we are building it using webGL which may take some time
all the basic commands and raster/vector display can be done.
If anyone is intersted will share the source under same license are GRASS GIS.
http://grass.osgeo.org/wiki/WebGRASS
Regards,
Rashad