not so sure that is correct. ms sql WAS sybase from 1989 until the fork in 1993 and i have been told that substantial changes to the codebase did not occur until years after the 1993, during the jim gray tenure.
Our Vendor offered Sybase in the mid 200x's as a choice for our college middleware, but they used 'case-insensitive' sort, which the linux version of Sybase did not work with.
Sybase, Ingres