When a controller comes out of the box you can do normal "full-setup" whatever what firmware (sd-branch or campus) is used.
When subscribed the licence an provisioned in Aruba Central, Central will push de SD-Branch firmware version (it's not manual downloadable on the ASP website).
When it was configured to Aruba Central SD-Branch and you want to go back to Campus mode, just do a "write erase all" on the controllers and (quickly;) de-subscribe the licence in Aruba Central so it will not be automatic configured through activate.arubanetworks.com ;).
After do the "full-setup" again, mentioned that the SD-Branch firmware can't run a commando like "show switchinfo". At this point you need to load the campus firmware which can be download from asp.arubanetworks.com website.
(host)# copy ftp: <ftphost> <ftpusername> <image filename> system: partition <0|1>
or
(host)# copy tftp: <tftphost> <image filename> system: partition <0|1>
or
(host)# copy scp: <scphost> <scpusername> <image filename> system: partition <0|1>
Iam not sure what firmware is used out-of-the-box, but i think its the campus firmware because de SD-branch firmware is pushed from Aruba Central after provining.
In my HomeLAB i have 2x9004 in Campus Mode with ArubaOS 8.6.0.5 (L2 Clustered).