I think this is an incorrect answer: see SQL Server 2000 Failover Clustering which points out that although Windows Server 2003 Enterprise edition supported up to 8 nodes, SQL Server cluster could not be inctalled on a system with more than 4 nodes. There was also a SHILOH bug notice reporting this.
The bug may have been fixed some time later, but apparently hadn't been fixed when this question was published, as the revision of the BoL page mentioned above that took place 11 months after this question still had the same statement in it.