It would be nice to support log4j's NDC class.
For example http://opensaml.org depends on that.

It is a straight forward port that simply delegate all log4j's NDC calls to slf4j's NDC static methods.

This commit http://github.com/hmalphettes/slf4j/commit/2d30df3bd74e920d505308b322579d6fbbb4e1ab
Does add such support and behaves well with opensaml.

I also found a missing Import-Package in log4j-over-slf4j's MANIFEST for OSGi.
org.apache.log4j.Log4jLoggerFactory requires org.slf4j.helpers.Util

Cheers,
Hugues.