The ethical principles that motivated the creation of these licenses are presented. Unlike licenses that seek to lock up software in a proprietary fashion, the GPL and LGPL are designed to grant freedom to innovate, learn and improve. Those principles influence licensing policy decisions. We present the specific definition of the concept of “Free Software” (software whose license grants freedoms to copy, share, modify and redistribute the software either gratis or for a fee) for for-profit companies.

The preamble presents the intent of the license. The preamble puts forth the motivations for the detailed terms and conditions that follow in the license. We discuss the language of the preamble in detail to show how it frames the legal details that follow.

GPL's Section 0 defines and presents the terms that make the basis of this copyright license. We discuss those definitions and the copyright scope of the license.

Section 1 defines the terms for making source-only copies of software programs. We discuss how those rules work and the requirements and obligations for distributors of GPL'd source, whether they choose to distribute at no charge or for fees.

Free Software licensing in general, and the GPL and LGPL in particular, relies critically on the concept of derivative work since software that is independent (i.e., not derivative) of Free Software need not abide by any of the terms of the applicable Free Software license. If a work is a derivative work of Free Software, then the terms of the license are triggered, and one has obligations to comply with the terms of the Free Software license under which the original work is distributed. Therefore, one is left to ask, just what is a “derivative work?” We will show how the answer to that question depends on which court is being asked. We also present the best background information available to build a working understanding of what is generally considered a derivate work in the rapidly changing field of software copyright law.

Section 2 sets forth the rules for creation of derivative works of GPL'd software. We discuss the intent of this section of GPL and how it relates to the copyright situation discussed in our discussion of derivative works. We also explain the details of preparing derivative source in a GPL-compliant way.

Source-only distribution works well for technically savvy clients and users, but most want runnable binary programs as well. Section 3 gives permission for the creation and distribution of such binary works. We explain how GPL's requirement for corresponding source code operates, and detail what distribution options are available to distributors of binary GPL'd software. We explore the benefits and downsides of each of those options.

Patent rights are most often granted expressly, through detailed language in a license. However, express patent grants are not the exclusive way rights in patents are granted by patentees. Even without express language, patent rights can be granted by a patentee's actions or behavior. The GPL contains no express patent grant. Does that mean it grants less rights in the licensor's patents than other licenses which do? Or, does the GPL, in its silence, actually result in a grant of patent rights to the licensee greater than what occurs through many other Free Software and “Open Source” licenses?

We will consider these questions and provide detailed answers to them.

Section 4 terminates rights under the GPL for those who violate it. We discuss how such termination works, what it means for violators, what risks one takes in violating, and how rights are typically restored. We briefly mention how Section 4 is used as the central tool in GPL enforcement.

GPL is not a contract, so acceptance of the license works differently than it does for contracts. We discuss how this acceptance works under the copyright rules that govern the GPL.

Other licensing terms cannot be placed on GPL'd software that would trump the rights granted under GPL. We discuss how Section 6 is used to ensure that no such additional restrictions occur. We briefly discuss how this leads to the concept of GPL-incompatible Free Software licenses.

Just as additional licensing restrictions cannot trump the GPL, outside agreements, patent licenses or court orders cannot do so either. We discuss how Section 7 ensures that other rules outside of the direct software license cannot take rights away from users, distributors, and modifiers of GPL'd software.

Section 8 is a rarely used part of the GPL that helps copyright holders when certain technologies are prohibited from full international distribution due to draconian rules elsewhere in the world. We explain how Section 8 helps such copyright holders.

We discuss how the update process and release of new GPL versions happens.

Section 10 reminds licensees that under copyright law, other relicensing arrangements can be made. We discuss how this can often be used as a business model and we explicate that model's benefits and downsides.

Almost all software licenses, including Free Software licenses such as the GPL, contain sections, typically in all caps, regarding warranties and liability. The purposes of these sections are lost on most non-lawyers, but attorneys understand the importance their language provides to both the licensor and the licensee. Some have argued that the GPL's Sections 11 and 12 render it entirely unenforceable. We consider whether that is true, and present the likely interpretation and implementation of the GPL's Warranty Disclaimer and Liability Limitation provisions.

The LGPL is a “scaled back” version of GPL, designed specifically to allow creation of a very well-defined class of proprietary derivative works. However, it does prohibit turning the LGPL'd software itself directly into proprietary software.

We discuss the basic design of LGPL and how it compares and contrasts with GPL. We introduce the two classes of derivative works covered by LGPL, “works that use the library” and “works based on the library,” and give some concrete examples of what proprietary derivative works are prohibited and permitted when basing the software on an LGPL'd work.