The adoption of the Internet technologies favors the diffusion of Web and grid-based applications. However, the development of new applications exploiting the modern interfaces and distribution channels have to face the problems connected with the integration of existing software systems. This aspect often requires the migration of legacy systems toward the Web technologies, as they are very important for the business they support and cannot be simply discarded. In fact, they encapsulate a great deal of knowledge and expertise about the application domain. Many migration strategies have been proposed in the literature. The introduction of dynamic activation and discovery of services is rarely considered in the proposed approaches, even if these aspects can be considered as important evolution factors for the future of the legacy systems. With this in mind, this paper extends an approach, already proposed by the authors for migrating to the Web legacy software systems with character-based user interface, with grid technologies.