There is actually little relationship between the two projects. I wrote Gravel as a supplementary tag library for the jBPM web console project. Because of the general usefulness of the tags, I made it its own project so that other people can take advantage of the functionality.
Gravel does not provide any UI "components" per se - it mostly provides a number of utility tags to make some tasks easier, like better action handling and navigation (compared to the standard JSF stuff), GET variable processing, etc. Also I provide a handy set of tags that wrap the HTML tag of the same name, but provide extra features like the rendered="" attribute, standard JSF ID generation (including support for NamingContainers like <h:form>), and the ability to suppress the tag rendering (but retain the tag content).
Also there's an alternate implementation of dataTable that actually replicates the components in each row rather than rendering each component multiple times, as the standard <h:dataTable> does.
There's a few other useful components in there too. Basically it's useful for any Facelets project where you need these basic tags that were not included with JSF to begin with. (Note that Gravel *only* works under Facelets.)
great, ty for your answer, ill try to use Gravel, sounds like a nice idea.