Extending the comment from Daniel, we know the "alternative" is to use the MSFT JDBC driver for SQL Server (which is JDBC 4 compliant). However, our tests with EAP 6.0.1 (well not EXACTLY EAP 6.0.1, but rather this: https://github.com/hasalex/eap-build which patches the maven build to pull the dependencies from the public repositories rather than the *-redhat-1 repositories), we noted considerable performance differences between the jdts and the msft driver:
On a specific page in our app (ejb3, hibernate, wicket 6, running on the same server, connecting to the same DB) doing a large number of select statements, the msft jdbc driver was a factor of 1,5+ slower (2,3 vs 3,8 sec.).
The the following thread on the jdts site and general feedback from the community also seem to speak against this:
Measurably poor performance with our app, "flaky" network performance, thread locks, etc. mean that the msft driver is not a real alternative for our systems.