I guess this is caused by a transitive recommended dependency. The recommended dependencies of libactivemq-java are indeed optional, but one of the libactivemq-java dependencies probably has a recommended dependency that is actually required.
Emmanuel Bourg __ This is the maintainer address of Debian's Java team <http://lists.alioth.debian.org/cgi-bin/mailman/listinfo/pkg-java-maintainers>. Please use [email protected] for discussions and questions.

