Tight Open Core is a model where the software has its primary functionality covered under an open source license (the “core”), but has direct (often critical) features that are only available under a proprietary license.
Take, for example, the feature of authentication and authorization. Some amount of these are critical for almost all software. In a Tight Open Core model, this functionality will not exist in the open source core: instead, it will be pushed to either proprietary plugins or exist only in fully proprietary builds.
Frequently used by venture backed startups, with a single company putting in the bulk of the engineering and product resources. The goal is to have successful enough core offering to generate substantial demand for the proprietary functionality.
These types of software are usually intended to be monetized from the beginning, although some (like Elastic) have shifted to this model over time. With this model, it is easier to determine if a given piece of functionality should be in the core or not: if it is critical to the success of your target market, it should be proprietary.
No. There is evidence it is more effective as a business model than its cousin, loose open core. However, the dynamics of keeping vital functionality out of the core means that, should the community decide to replicate the feature, it is directly at odds with the company’s monetization model.