Countly vs Datamuse

Countly is an open-source product analytics platform you self-host (or run as their managed cloud), ingesting events over a REST Data API keyed by a per-app `app_key` rather than a private secret — a live unauthenticated POST to a running Countly server (try.count.ly/o) confirmed the endpoint only demands `app_key`, returning a `missing_api_key` JSON error otherwise. The Community Edition is free and self-hostable under an AGPLv3-derived license; Countly also sells a paid Enterprise Edition with SSO, extra data sources, and dedicated support.

Datamuse is a free word-finding query engine for autocomplete, rhyme, and meaning-based lookups; a live unauthenticated GET against `api.datamuse.com/words` returned a 200 JSON array with `Access-Control-Allow-Origin` echoing the request Origin plus `Access-Control-Allow-Credentials: true`, resolving cors "unknown" to "yes". Its own homepage now states that starting January 1, 2027 an API key will be required on every request (capped at 100,000/day per key) after more than a decade of fully free access — as of this check the API still works with no key at all.