According to the Amazon Web Services (AWS) site, you can now use DB2, Informix, WebSphere sMash, WebSphere Portal Server or Lotus Web Content Management on Amazon's EC2 cloud.
"This relationship will enable you to bring your own IBM licenses to Amazon EC2, utilize IBM’s 'Development' AMIs, or leverage the 'Production' Amazon EC2 running IBM service. All of these options will enable you to get started quickly using popular IBM platform technologies in the Amazon EC2 environment."
To me, this move was clearly focused at besting Microsoft's Azure platform into the cloud and represents a huge leap forward for this nascent industry. Now an enterprise can easily use these IBM products as a utility. As IBM adds more of their products into the mix, cloud transition offerings (enterprise-to-cloud or cloud-to enterprise) will follow.
This also represents a huge turning point for cloud interoperability. IBM's enterprise footprint paired with Amazon's established lead in infrastructure-as-a-service could create a de facto standard within the cloud computing community.
I'm not sure if this is good or bad, but it is definitely a huge event.