Yes, but with some limitations.
The SQL Server JDBC driver is available directly from Microsoft at their website.
Currently the SQL Server 2005 JDBC Driver 1.2 is recommended (we've been using it during testing).
The version 2.0 should also work correctly.
If you are offered a choice of download versions we suggest choosing the Unix rather than Windows version. (Because it easier to extract)
The unix edition is provided as tar.gz file and can be easily decompressed.
The archive contains a folder called enu which contains a file called sqljdbc.jar
This file sqljdbc.jar should then be copied into /Library/Java/Extensions/
SQLEditor should find these drivers automatically when it starts up.
If SQLEditor is already running you may need to restart it to see the new drivers.