In the earlier days of FreeTDS, Microsoft did not release official specs for the TDS protocol. When MSSQL 2000 (product 8.0) was released, there was semi-official indications from the Microsoft community that the TDS protocol would be version 8.0. So the FreeTDS developers adopted that version for FreeTDS. Years later, when Microsoft started releasing official specs of the protocol, it became obvious that the TDS versions that FreeTDS had labeled 8.0 and 9.0 were actually versions 7.1 and 7.2 respectively.