From Aventine Solutions

Clover ETL is a commercial open source solution in the business intelligence space for doing Extract/Transform/Load. "Commercial" open source is this case means that ETL modules can be built using the base framework, without cost, by coding in a text editor and compiling or the GUI component can be purchased which speeds up the development with graphical components and wizards. In any case, the source code for the framework is provided with LGPL while the commercial GUI component licensing allows for commercial, evaluation and academic usage of the product.

Clover seems to be a good choice for J2EE projects where reporting and business intelligences is often (at least by my experience) an afterthought and the budget does not allow for extra, expensive business intelligence consultants. If the team is using Eclipse, Clover is a natural fit and the Java Programmer will feel at home with the various ways that ETL components can be built. On the other hand, if the enterprise is big enough to already have a separate business intelligence or data warehouse team that are used to some platform specific tools for ETL, then Clover would probably seem obtuse and clumsy.

[edit] The First Transformation, Step for Step

For the first transformation, I tried something very straightforward with a single JDBC source database query into a single datawarehouse database input table using a single ReformatTransformation.