Are AI Agent Engrams Open Source or Proprietary?

Are AI Agent Engrams Open Source or Proprietary? The short answer: both, and the split matters. The major agent-memory engines — Mem0, Letta, Cognee, Graphiti, LangMem, and PLUR — are all Apache-2.0 or MIT licensed on GitHub. But "open source" and "open format" are not the same thing. A project can ship under Apache-2.0 while storing your memories in opaque vector blobs you cannot read, edit, or export. The real question is not whether the software is open — it usually is — but whether your memories are. This distinction separates the field into three tiers: fully open (software + format + data you own), open-core (software is open, but the hosted memory is not portable), and fully proprietary (memory baked into a model provider's infrastructure, no export at all). Why this question exists AI agents face a brutal constraint: they forget. Every new session starts blank. Every context window overflows. The fix is persistent memory — but persistent where, and in whose format? The term "engram" comes from neuroscience. Richard Semon coined it in 1904 for the physical trace a memory leaves in biological tissue (Semon, 1904; cited in Wikipedia, "Engram (neuropsychology)"). Applied to AI agents, an engram is one discrete thing an agent has learned — a correction, a preference, a procedure — stored so it survives across sessions. The question "open source or proprietary?" asks two things at once: Is the engine that stores and retrieves engrams open source? Is the format those engrams are stored in open — readable, editable, portable? Conflating the two is how vendors end up with open-source repos and locked-in data. Tier 1: Fully open — software, format, and data These projects ship under permissive licenses (Apache-2.0 or MIT) AND store memory in a format you can inspect, edit, and export. Project License Stars (Jul 2026) Memory format Data ownership PLUR Apache-2.0 ~215 Human-readable YAML engrams Yours — plain files PLUR stores each engram as a plain-text YAML entry — an