Wow! That really goes back. Yes, the first MS version of SQL Server was to take Sybase and port it to run on OS/2.

I am not sure, but as I recall, version 4.21 was the first version to run under the Windows OS (Window NT Advanced Server was the branding as I recall).

Version 4.21a was the first version of SQL Server to break away from Sybase as a purely MS code base.