Open-core model

The open-core model is a business model for the monetization of commercially produced open-source software. Coined by Andrew Lampitt in 2008, the open-core model primarily involves offering a "core" or feature-limited version of a software product as free and open-source software, while offering "commercial" versions or add-ons as proprietary software. The concept of open-core software has proven to be controversial, as many developers do not consider the business model to be true open-source software. Despite this, open-core models are used by many open-source software companies. Some open-core products require their contributors to sign a contributor license agreement, which either dictates that the copyright of all contributions to the product become the property of its owner, or that the product's owner is given an unlimited, non-exclusive license to use the contributions, but the authors retain copyright ownership. In an open-core scenario, these agreements are typically meant to allow the commercial owner of the product (which in some cases, is ultimately the copyright holder to all of its code, regardless of its original author) to simultaneously market versions of the product under open-source and non-free licenses. This is in contrast with more traditional uses of CLAs, which are meant solely to allow the steward of an open-source project to defend and protect the copyrights of its contributors, or to guarantee that the code will only ever be made available under open-source terms (thus protecting it from becoming open core). Kafka, a data streaming service under the Apache 2.0 license, is the open-source core to the company, Confluent, which issues a Confluent Community License, a source-available license that governs additional features in the Confluent Platform. Cassandra, an open-source database under the Apache 2.0 license, is the core to the company, Datastax, which issues enterprise subscription license for additional management and security features inside DataStax Enterprise.