Unique among software licenses, Open Source Software (OSS) licenses actually originated with developers rather than lawyers and must be recognized by the Open Source Initiative to truly be considered ‘open source’.
Typically, software licensing is designed to protect the intellectual property rights of software owners, however the objective of Open Source licensing is to protect the open distributability of the software.
Common aspects of OSS licensing include:
Open Source licensing structures are classified as either Restrictive or Permissive, others somewhere in between. The classification is based on the distribution intent of the original owner.
Restrictive licenses are preferred by projects who want to ensure the future openness of a project; they restrict the ability to make a derivative project’s code proprietary. Restrictive licenses require derivatives, improvements, or enhancements to be made available under similar terms. Examples of restrictive licenses are Copyleft, reciprocal licenses and the GPL.
Permissive licenses are often preferred if a project needs to protect trade-secrets or is intended for a secure environment. Although the licensing of the original project remains in force, modifications and enhancements may become proprietary. The distribution of code is permitted provided copyright notice and liability disclaimer are included and contributors’ names are not used to endorse the new product. Examples of permissive OSS licenses include the Berkeley Software Distribution (BSD) license and the Apache Software License.