Seems to be dead? I went to report the misspelling of Columbus, Ohio, and discovered there's been an open ticket for 5 years. https://github.com/stevage/OpenTrees/issues/58
Is it "dead"? Hmm. It's complicated. It's true the data hasn't been updated in a long time. The biggest issue is that most of the data sources that were present on OpenTrees are no longer online.
So if I do a fresh harvest and rebuild, a lot of that data will disappear, which is a bit sad.
I'm in two minds about what to do, and have been for a long time.
So, it's not "dead", it's just very indecisive.
Could also be cool to try to somehow load some of this data into OpenStreetMap -- then if the sources go away, local mappers can potentially pick up the torch.