Is it possible to scrape the basemap in this webmap (just the georeferenced boundaries) using any software?
Indeed looking at the layers and the functionalities provided on the interface you cannot get the result you desire from this app. However in QGIS you may load Google Physical or any base map and if your boundaries of interest are shown clearly you can create a new shapefile and digitize your polygons.NB: First install OpenLayers plugin to access base maps. Unfortunately this seem not to be the case with your area of interest when I checked. You can only get the boundary for Kerala and not subdivisions within. The boundaries are not showing on Google maps and you will probably have to acquire those measured parcels from somewhere in your country.