Just by experience, trojans aren't terribly hard to make. If he's got any programming knowledge, he probably could have built his own trojan that does that for LINUX and another for Win(Whatever). Then, since he made it, he probably made it to accept any certain signal, maybe some dos command. Therefore, he puts it on each computer and can cause each to pop its CD drive open at any time. Since he made it, the only function was probably the CD-eject.