How to convert SQL Server .MDF database to Mac OS PostgreSQL database on Mac OS X? I need to import a SQL Server database which is in the .mdf format into a PostgreSQL database. My system is Mac OS X.

How to do it in the easiest way?
You'll need to attach the database to a Microsoft SQL Server database, the export the data into the Postgres database.  Assuming that you've got the Windows Postgres ODBC drivers handy you can use SQL Server's Import/Export wizard to copy the data into the Postgres database.