Windows Server and MS SQL would both require the Enterprise versions (Operating System and SQL) in order to support MSCS clustering. With CA XOsoft you can create a replication and high availability solution which would allow you to perform a switchover to an alternate host and redirect user and application traffic to the Disaster Recovery server without the need to run the Entperprise version of the OS and SQL.
In a CA XOsoft High Availability scenario for MS SQL the Disaster Recovery Server can be located remotely at an alternate physical site to protect in the event of an entire site outage. An MSCS cluster will not provide this level of high availability.