<P> However, software running as an application program under a GPL - licensed operating system such as Linux is not required to be licensed under GPL or to be distributed with source - code availability--the licensing depends only on the used libraries and software components and not on the underlying platform . For example, if a program consists only of own original custom software, or is combined with source code from other software components, then the own custom software components need not be licensed under GPL and need not make their code available; even if the underlying operating system used is licensed under the GPL, applications running on it are not considered derivative works . Only if GPLed parts are used in a program (and the program is distributed), then all other source code of the program needs to be made available under the same license terms . The GNU Lesser General Public license (LGPL) was created to have a weaker copyleft than the GPL, in that it does not require own custom - developed source code (distinct from the LGPLed parts) to be made available under the same license terms . </P> <P> The distribution rights granted by the GPL for modified versions of the work are not unconditional . When someone distributes a GPL'd work plus his / her own modifications, the requirements for distributing the whole work cannot be any greater than the requirements that are in the GPL . </P> <P> This requirement is known as copyleft . It earns its legal power from the use of copyright on software programs . Because a GPL work is copyrighted, a licensee has no right to redistribute it, not even in modified form (barring fair use), except under the terms of the license . One is only required to adhere to the terms of the GPL if one wishes to exercise rights normally restricted by copyright law, such as redistribution . Conversely, if one distributes copies of the work without abiding by the terms of the GPL (for instance, by keeping the source code secret), he or she can be sued by the original author under copyright law . </P> <P> Copyleft thus uses copyright law to accomplish the opposite of its usual purpose: instead of imposing restrictions, it grants rights to other people, in a way that ensures the rights cannot subsequently be taken away . It also ensures that unlimited redistribution rights are not granted, should any legal flaw be found in the copyleft statement . </P>

Which of the following is not a benefit of the open-source model