Final answer:
For using existing server-bound software licenses on AWS, EC2 Dedicated Hosts is the best option, as they provide physical servers dedicated for your use, enabling compliance with licenses that require a physical dedicated server.
Step-by-step explanation:
When moving a large application to AWS with existing server-bound software licensing, the best option is using EC2 Dedicated Hosts. This is because Dedicated Hosts allow you to use your existing server-bound software licenses and run them on AWS infrastructure. They give you physical servers that are dedicated for your use, which can help you meet compliance requirements that necessitate a physical dedicated server. EC2 Dedicated Instances also provide dedicated infrastructure, but they do not offer the same level of control over the physical server as EC2 Dedicated Hosts. EC2 Spot Instances and EC2 Reserved Instances are cost-effective solutions for different use cases, such as flexible start and end times or long-term commitments, and they do not accommodate the use of existing server-bound software licenses as effectively as Dedicated Hosts.