tl;dr: A former Meta engineer who helped build Mononoke, Facebook's open-source version control server, argues that Anthropic's newly announced Scion VCS heavily copies Mononoke's "derived data" design without crediting it—mentioning only Sapling for "hard-won lessons." The author doesn't object to the design being reused (that's the point of open source) but calls out Anthropic for implying Claude originated the ideas. He warns that as LLMs increasingly draw on existing open-source designs, properly crediting prior art becomes both easier and more essential.