Open source

Open source refers to a software license where source code access is regulated by set of published principles. There are many such licenses.

Free software is not considered open source because of the required reintegration clauses that "keep improvements free" for all users.

Consortium licenses sometimes qualify as open source, sometimes not.

A Green software license probably would not qualify, as it would restrict unpaid use to Green purposes and might forbid some uses entirely.

Shared source is not open source, as it is controlled tightly by one vendor, e.g. Microsoft.