The '-o' option specifies what version of Opscenter to download and install. As far as I can tell, it only works if you provide '--dse' when you create your CCM cluster. DSE and Opscenter support was only recently added, so it may be that no one has done the work to make it work for non-DSE setups.
Here's an example:
$ ccm create --dse -v 4.6.0 --dse-username=myusername --dse-password=mypassword -o 5.0.2 -n 3 dse460
Downloading http://downloads.datastax.com/community/opscenter-5.0.2.tar.gz to /var/folders/nw/5f2tsw817ln2smczw1hx_tx00000gn/T/ccm-NwRIFb.tar.gz (68.589MB)
71920484 [100.00%]
Extracting /var/folders/nw/5f2tsw817ln2smczw1hx_tx00000gn/T/ccm-NwRIFb.tar.gz as version opsc5.0.2 ...
Downloading http://downloads.datastax.com/enterprise/dse-4.6.0-bin.tar.gz to /var/folders/nw/5f2tsw817ln2smczw1hx_tx00000gn/T/ccm-1_ON_p.tar.gz (511.738MB)
536595851 [100.00%]
Extracting /var/folders/nw/5f2tsw817ln2smczw1hx_tx00000gn/T/ccm-1_ON_p.tar.gz as version 4.6.0 ...
Current cluster is now: dse460
$ ccm start
After my cluster starts Opscenter is running at http://localhost:8888 with all 3 agents connected.
Since CCM downloads and installs Opscenter Community Edition, it probably can be made to work without the requirement to run DSE. Since ccm is open source, that might be a nice feature that someone can add. I think it's useful so I may look into it unless someone else is already on it.