![]() ![]() And it positioned “free” (as in free to use, copy, modify, etc.) software (Tiny BASIC) against proprietary/copyrighted software (Microsoft’s Altair BASIC). That line didn’t have any legal power, but it was catchy (and pretty funny, if we do say so). ![]() Li-Chen Wang added this humorous text to the distribution notice of his Palo Alto Tiny BASIC programming language: "COPYLEFT ALL WRONGS RESERVED." The line was a dig at Microsoft co-founder Bill Gates, who had complained about software hobbyists pirating the company’s Altair BASIC program, which sold for $150 a pop at the time. The word “copyleft” was coined in direct opposition to the familiar term “copyright.” In 1976, developer Dr. In this blog, we’ll take a close look at copyleft licenses, including their history, how they compare to permissive licenses, and the difference between strong and weak copyleft licenses. For developers of free and open source software, copyleft is a way to ensure the software remains freely available. For developers of proprietary software, software under copyleft licenses must be used with care. That is a feature or a bug, depending on how you look at it. They also don’t have any such code-sharing requirement, so the “open source-ness” does not necessarily persist to the derivative work. One of the practical ramifications of this requirement is that OSS users may be forced to publish their own changes or additions in source code form if they release a binary that includes a copyleft-licensed component.Ĭopyleft licenses stand in contrast to permissive licenses, which tend to have few restrictions on use of the licensed code. In other words, the modified code has to be exactly as “open” as the original. GPL v2).īroadly, though, OSS licenses can be broken down into two categories: permissive and copyleft.Ĭopyleft licenses - the subject of this blog - generally require that any derivative work of the copyleft-licensed software be released under the same license as the original software. the Beerware License) to the classic (i.e. A typical example is a probabilistic automaton $\mathcal $ is a finite set of registers and are, respectively, the initial values and final coefficients of registers and is a deterministic transition function.There are hundreds of different open source software licenses in use today, with provisions ranging from the comical (i.e. finite automata, rational series, matrix representation or recently linear cost-register automata (linear CRA) . They have various equivalent presentations: e.g. Weighted automata are a natural model of computation that generalise finite automata and linear recursive sequences . Assuming Schanuel's conjecture is true, we prove decidability of universal coverability for three-dimensional OVAS, which implies decidability of zero isolation in a model with at most three independent registers. In standard VAS runs are considered only in the positive orthant, while in OVAS every orthant has its own set of vectors that can be applied in that orthant. We obtain a model, where zero isolation becomes equivalent to universal coverability of orthant vector addition systems (OVAS), a new model in the VAS family interesting on its own. There, we show that the boundedness problem is decidable.Īs for the zero isolation problem we need to further restrict the class. In the general model both problems are undecidable so we focus on the copyless linear restriction. The two problems of boundedness and zero isolation ask whether there is a sequence of words that converge to infinity and to zero, respectively. We consider linear cost-register automata (equivalent to weighted automata) over the semiring of nonnegative rationals, which generalise probabilistic automata. ![]()
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