Meanwhile their Tree-Sitter-based semantic parser[1] looks abandoned. There is even rotting for years pull request[2] adding support of the same stack graphs into it.
As mentioned elsewhere on this thread, stack graphs and Semantic were built by the same team (which I manage). Semantic is not abandoned, we've just been focusing on a different layer of our tech stack for the past year or so. https://news.ycombinator.com/item?id=29501389
That PR on the Semantic repo was our first attempt at implementing these ideas. We decided to reimplement it in a separate library (also open source, https://github.com/github/stack-graphs), which only builds on tree-sitter directly so that there's an easier story for us and language communities to add support for new languages. It's a fair point that we could have closed the Semantic PR to indicate that more clearly.
[1] https://github.com/github/semantic
[2] https://github.com/github/semantic/pull/535