Software license pricing varies widely between software vendors that offer complete on-premises business solutions, as opposed to those that provide open source objects for building internal applications and web functionality. While these costs may seem unnecessary, just like an insurance policy, it offers protection when you actually need it. If the software is defined as in the public domain, everyone is free to use and modify the software without restrictions. This is a „permissive“ license that allows you to take the code into applications or projects and reuse the software at will. A software license agreement, also known as an „end user“ license agreement, is a legally binding agreement between the owner of the proprietary software (in this case, your company) and the end user (your customer). The Agreement describes how the Software may or may not be used, in addition to a summary of the User`s rights under U.S. federal law. These agreements are usually displayed when the user installs software and require the user to click „Accept“ to access the software. Ownership of digital assets such as software applications and video games is challenged by the „licensed, unsold“ EULAs of digital distributors such as Steam.
 In the European Union, the Court of Justice of the European Union has ruled that a copyright owner cannot refuse to resell software sold digitally under the rule of exhaustion of copyright on first sale upon transfer of ownership, and therefore challenges the EULA „licensed, not sold“.       UsedSoft, based in Switzerland, has innovated in the resale of enterprise software and fought for this right in court.  In Europe, EU Directive 2009/24/EC explicitly allows the trade in used computer programs.  An example of a free software license with copyleft is the often-used GNU General Public License (GPL), also the first copyleft license. This license is intended to give and protect all users unlimited freedom to use, study, and modify the software privately, and if the user complies with the terms of the GPL, the freedom to redistribute or modify the software. For example, all changes made and redistributed by the end user must include the source code of the changes, and the license of a derivative work must not impose additional restrictions beyond what the GPL allows.  The caveat is that if any part of the library is copied or modified into the code, the terms of the original LGPL license apply to the developed code that used the library. Most distributed software can be classified by license type (see table).
Under an LGPL license, developers have the right to link to open source libraries in their own software. The resulting code can be licensed under any other type of license, even proprietary, when projects are compiled or linked to include an LGPL licensed library. Software licenses are generally proprietary, free or open source, the distinguishing feature being the conditions under which users may distribute or copy the software for future development or use. Between these two extremes, there are also three categories (GNU/LGPL, permissive, and copyleft) that apply to different forms of open source projects. Failure to comply with the terms of an open source license can result in the disclosure of trade secrets or even legal action by project developers. There are several organizations in the field of open source software that issue policies and definitions regarding software licensing. The Free Software Foundation maintains non-exhaustive lists of software licenses according to its definition of free software and licenses that the FSF considers non-free for various reasons.  The FSF also distinguishes between free software licenses that are compatible or incompatible with the FSF license of choice, the COPYLEFT GNU General Public License. The Open Source Initiative defines a list of certified open source licenses based on their open source definition.  The Debian Project also has a list of licenses that follow its Debian free software guidelines.  Two common categories of software that are subject to copyright and therefore contain licenses that grant the licensee certain rights are proprietary software and free and open source software (FOSS). The distinct conceptual difference between the two is the granting of rights to modify and reuse a software product purchased from a customer: FOSS software grants both rights to the customer and therefore aggregates the editable source code with the software („open source“), while proprietary software generally does not license these rights and therefore keeps the source code hidden („closed source“).