See fuse forum
I think there is an optional AMQ dependency which needs to be installed to support the XStream stuff.
I looked at the features from Fuse ESB
[installed ] [4.3.1-fuse-01-09 ] activemq-broker repo-0
[installed ] [5.4.2-fuse-03-09 ] activemq activemq-5.4.2-fuse-03-09
[uninstalled] [5.4.2-fuse-03-09 ] activemq-spring activemq-5.4.2-fuse-03-09
[installed ] [5.4.2-fuse-03-09 ] activemq-blueprint activemq-5.4.2-fuse-03-09
[uninstalled] [5.4.2-fuse-03-09 ] activemq-web-console activemq-5.4.2-fuse-03-09
And I couldn't see any optional.
We do release the optional JARs