It is being developed by a Harald Hanek, initially for his daughter and now under GPL for us all. In his own words he describes Gollum as such, “Gollum is a Wikipedia Browser for fast and eyefriendly browsing through the free encyclopedia ”Wikipedia“.
Gollum gives you access to nearly all Wikipedias in all languages. Further more Gollum gives you some special features which allow you to easily customize your work with Wikipedia.
In my opinion the interface of Wikipedia is too overloaded and confusing. So let’s get an easy to use interface. Gollum, the intuitive way to the powerful knowledge of Wikipedia.”
As you can see the navigation is nice and easy and the content is displayed in a very readable format. It loads pretty fast too, and has good localizations.
It is soon to be available as a beta download.