From OpenKM Documentation
Download SQL Server JDBC driver from Miscrosof SQL Server Driver Page and move it to $JBOSS_HOME/server/default/lib if you have OpenKM-5.X and $TOMCAT_HOME/lib for OpenKM-6.X.
|Other JDBC driver for MS SQLServer we've tested is jdts.|
|OpenKM 6.2 has been verified to run with SQL Server 2005 using the JDBC driver sqljdbc4.jar under tomcat-7.0.27|
|OpenKM 5.0 has been verified to run with SQL Server 2005 using the JDBC driver sqljdbc.jar under JBoss 4.2.3.|