You can make a
backup alright... but you won't be able to burn it back to a CD at this time with nearly all consumer-grade CDRW drives.
The bleemcast people managed to come up with some very tricked-out copy protection scheme involving audio tracks of extremely short length (AFAIK), so a drive will flat out refuse to burn the image back to a CD.
Nobody has managed to work around it yet, as the bleemcast emulator checks for those offbeat tracks or sectors very closely, and refuses to run if it finds the CD isn't the original bleemcast disc.