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Open-source software is published with its source code, the human-readable instructions programmers write, under a licence that lets anyone study, change and share it. Linux, the Firefox browser and MediaWiki, which runs Wikipedia, are all made this way.

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Sharing code was normal in the early days of computing. In the 1980s, as most software became closed, Richard Stallman started the free software movement. In 1991 Linus Torvalds released Linux, which now runs most of the world's busiest web servers and all of the 500 fastest supercomputers; Android is built on it too. The term 'open source' was suggested by Christine Peterson in 1998 to make the idea appealing to business, and the Open Source Initiative was founded the same year. Licences differ. Permissive ones, such as MIT or Apache, let others reuse the code almost freely, while 'copyleft' ones, such as the GNU GPL, require anyone who passes on a changed version to share it under the same terms. Projects are run by volunteers, companies or both.

Türkçe oku
Açık kaynak yazılımlar kaynak koduyla, yani programcıların yazdığı, insanların okuyup anlayabildiği komutlarla birlikte yayımlanır. Lisansları, bu kodu herkesin incelemesine, değiştirmesine ve paylaşmasına izin verir. Linux, Firefox tarayıcısı ve Wikipedia'yı çalıştıran MediaWiki de böyle yazılımlardır.

Bilgisayarların ilk yıllarında kod paylaşmak olağan bir şeydi. 1980'lerde yazılımların çoğu kapalı hâle gelince Richard Stallman özgür yazılım hareketini başlattı. Linus Torvalds'ın 1991'de yayımladığı Linux, bugün dünyanın en yoğun web sunucularının çoğunda ve en hızlı 500 süper bilgisayarın hepsinde çalışıyor; Android de Linux üzerine kurulu. “Açık kaynak” terimini 1998'de Christine Peterson önerdi; amaç, fikri şirketlere daha çekici göstermekti. Açık Kaynak Girişimi (Open Source Initiative) de aynı yıl kuruldu. Lisanslar birbirinden farklıdır. MIT ya da Apache gibi esnek lisanslar, kodun neredeyse hiçbir koşul olmadan yeniden kullanılmasına izin verir. GNU GPL gibi “copyleft” lisanslar ise kodu değiştirip dağıtan herkesin, yeni sürümü de aynı koşullarla paylaşmasını şart koşar. Projeleri gönüllüler, şirketler ya da ikisi birlikte yürütür.

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Background reading: Open-source software
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