Couchbase Server and Apache CouchDB are both open-source, document-oriented database systems, but they exhibit distinct differences in architecture and features. Couchbase Server functions as both a key-value and document store, supports SQL-like queries through N1QL, and offers features such as strong consistency, integrated caching, and cross-datacenter replication. It is designed to operate as a distributed cluster with automatic failover and master-master replication, with its development led by Couchbase Inc. Apache CouchDB, on the other hand, is a pure document store that emphasizes eventual consistency and operates with individual nodes containing full copies of data, using JavaScript-based views for querying. It supports master-master replication but lacks integrated caching and automatic failover, and is developed by a community of developers using Erlang. Both systems are licensed under Apache 2.0, and while Couchbase Server provides various official SDKs and connectors for integration, CouchDB relies on community-supported libraries.