Is it true that Bt brinjal seeds are sterile after one harvest, forcing farmers to buy seed for every planting?

There is no truth in this statement. Bt brinjal will be available as open pollinated varieties that will reach the farmers at low cost through a public distribution system by the various agricultural universities and research institutions involved in the project. These varieties will be qualitatively the same as existing varieties currently grown by the farmers apart from immunity to FSB. Farmers can save seeds from their harvest for planting future generations, and indeed will be encouraged to do so. For hybrids, as is the case currently for non-Bt brinjal (and indeed any hybrid cultivated crop), the farmers do indeed source fresh seeds from the private sector year after year. This is because hybrid varieties do not breed true, so second-generation plants do not have hybrid advantages and are less useful for planting.