As Hexabus requires IPv6-support of the kernel (which is not given in the stock firmware) a kernel update is required to add Hexabus on the Flukso. Therefore this is not done automatically and you have do a manual update of your Flukso. The code for the modified image is in a seperate branch (hexadaemon) on github.
You can download a precompiled image with support for Hexabus at http://openwrt.mysmartgrid.de/.
To flash the image follow the steps described at fluksov2update with the downloaded image files.
Hexabus-support for the Flukso adds a daemon to the Flukso that broadcasts the current measurements the to Hexabus network. In addition it listens for request from the Hexabus network such that the Flukso appears to be an ordanary Hexabus device.