Only when you look at it on the surface, does TrailBlazer seem the same as MosaicG. It's just similar in a few regards, specifically visual aspects. Our interface came from figuring out what users remember about the pages they visited, how they get back to them, and how to make this easier for the user.
Users usually remember the general path in which they took to get to a page, so showing the hierarchy allows them to find these paths and get to their destination with out re-traversing every page. TrailBlazer highlights the path when a person arrives at a member of that path, so that at a later date users can re-pickup the path and finder their destination. Users remember how a page looks and not necessarily logos, so we have full large thumbnails of the last seen portion of the page. Users remember relatively when they visit pages so we order paths top to bottom chronologically.
Most importantly users remember the CONTENT of the pages so we have summaries generated and index the pages so you can filter your history in real-time by content, thus displaying only the paths that pertain to what you are looking for. All nodes in those paths become subtly smaller and de-saturated so you don't lose your bearing and can find related pages.
The only thing MosaicG shares out of that design is that the pages are shown hierarchy, but even then, they are displayed quite differently. MosaicG makes the most recent pages larger, while TrailBlazer orders them by the time you access. There's a very good reason why both projects chose to layout their hierarchies in there respective ways.
MosaicG had a different design philosophy, they were trying to make sense of the web that people were browsing at that moment. We (with TrailBlazer) were trying to empower people to easily return to pages that they don't visit often, but do know about and want to get back to.
The final and very important detail when comparing TrailBlazer and MosaicG, while the screen shots may fool you, is that TrailBlazer is a GLOBAL history and MosiacG's history is a SESSION history. Which makes a BIG difference in their use.
MosaicG was limited by the technology of the time and they even mention that in their paper, so maybe TrailBlazer's design is an evolution rather than an revolution, as it's not the first graphical history, but that doesn't mean it's not new or not innovative.
- Jay Tuley