Rhino apparently is  a byproduct of Netscapes abandoned Javagator project that also produced Grendel both are related to Mozilla in that they have been continued as open source projects under the auspices of mozillaorg but it looks to me like Mozilla itself uses the Cbased SpiderMonkey for its JS engine  I certainly think Thunderbird is misplaced here in fact I think the subprojects and spinoff browsers sections need reorganisation and possibly merging  certainly they should be next to each other rather than with other sections in between Perhaps Mozilla technology could mention the structure of the suite itself and then a Related projects section could deal with Development tools bugzilla tinderbox bonsai etc Geckobased browsers whether they be geckoGUId or just geckorendered Projects based on Mozilla code thunderbird sunbird XMLTerm et al Other projects hosted by mozillaorg rhino grendel ElectricalFire Mstone although its hard to tell where on the scale from active to abandoned these projects are  What think ye