我同意有关咨询律师的意见(尽管该律师知道软件许可问题)。在做这些事情(以及更多)时，它们的长度超过了GPL的两倍。尽管GPLv3是一个复杂的法律文档，但其设计目的是让软件开发人员阅读和合理理解。在http://copyleft.org/guide/上也有一个了解它的指南以及对从v2到v3的更改的深入讨论。
GPLv3 of June 29, 2007 contains the basic intent of GPLv2 and is an Open Source license with a strict copyleft (→ What types of licenses are there for Open Source software, and how do they differ?) However, the language of the license text was strongly amended and is much more comprehensive in response to technical and legal changes and international license exchange.
The new license version contains a series of clauses that address questions that were not or were only insufficiently covered in version 2 of the GPL. The most important new regulations are as follows:
a) GPLv3 contains compatibility regulations that make it easier than before to combine GPL code with code that was published under different licenses (→ What is license compatibility?). This concerns in particular code under Apache license v. 2.0.
b) Regulations concerning digital rights management were inserted to keep GPL software from being changed at will because users appealed to the legal regulations to be protected by technical protective measures (such as the DMCA or copyright directive). The effectiveness in practice of the contractual regulations in the GPL has yet to be seen.
c) The GPLv3 contains an explicit patent license, according to which people who license a program under the GPL license both copyrights as well as patents to the extent that this is necessary to use the code licensed by them. A comprehensive patent license is not thereby granted. Furthermore, the new patent clause attempts to protect the user from the consequences of agreements between patent owners and licensees of the GPL that only benefit some of the licensees (corresponding to the Microsoft/Novell deal). The licensees are required to ensure that every user enjoys such advantages (patent license or release from claims), or that no one can profit from them.
d) In contrast to the GPLv2, the GPLv3 clearly states that there is no requirement to disclose the source code in an ASP use of GPL programs as long as a copy of the software is not sent to the client. If the copyleft effect is to be extended to ASP use (→ When does independently developed software have to be licensed under the GPL?), the Affero General Public License, Version 3 (AGPL) must be applied that only differs from the GPLv3 in this regard.
