The Jaguar handles memory differently when the CD player is connected; therefore games must be designed differently when created for the CD format. Programmers have claimed that if BattleSphere (or other games) were re-written for CD it would require a large amount of time. The only game that exists on both CD and ROM is Iron Soldier 2; I understand that both versions were developed simultaneously but separately.
Also, the encryption key method for CD games was 'lost' by Hasbro, and unlike the ROM cart encryption method, no one knows how to recreate it.
Carl from Songbird said just last night in the JFPN that he is working on a special cart that would allow Jag CDs to read unencrypted disks. You might want to read that for more details.
http://www.islandnet.com/~brclarke/jag_chat.htm
