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Opa (programming language)
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<p>Opa is a <a href="/facts/Programming_language/cWTYbgWa">programming language</a> for developing <a href="/facts/Scalability/jh7JomPa">scalable</a> <a href="/facts/Web_application/BLkF3BIN">web applications</a>. It is <a href="/facts/Free_and_open-source_software/1cHtjLCB">free and open-source software</a> released under a <a href="/facts/GNU_Affero_General_Public_License/n1h9A893">GNU Affero General Public License</a> (AGPLv3), and an <a href="/facts/MIT_License/8llAQtlk">MIT License</a>. </p><p>It can be used for both <a href="/facts/Client-side_scripting/psjqGKBx">client-side</a> and <a href="/facts/Server-side_scripting/JnLx8FnL">server-side scripting</a>, where complete programs are written in Opa and subsequently compiled to <a href="/facts/Node.js/FKzhV4Qa">Node.js</a> on a <a href="/facts/Server_(computing)/dEaYFD7r">server</a> and <a href="/facts/JavaScript/XhhIIEsl">JavaScript</a> on a <a href="/facts/Client_(computing)/u0wlVsWI">client</a>, with the <a href="/facts/Compiler/WNfCDFJe">compiler</a> automating all communication between the two. Opa implements <a href="/facts/Strong_and_weak_typing/WYexudnr">strong</a>, <a href="/facts/Static_typing/Tz0bAMS9">static typing</a>, which can be helpful in protecting against security issues such as <a href="/facts/SQL_injection/QD0cwbk5">SQL injections</a> and <a href="/facts/Cross-site_scripting/dhtusKKm">cross-site scripting</a> attacks. </p><p>The language was first officially presented at the Open Worldwide Application Security Project (<a href="/facts/OWASP/t30EKe8Q">OWASP</a>) conference in 2010, and the source code was released on <a href="/facts/GitHub/n1hNCsc3">GitHub</a> in June 2011, under a <a href="/facts/GNU_Affero_General_Public_License/n1h9A893">GNU Affero General Public License</a> (AGPL). Later, the license changed to the <a href="/facts/MIT_License/8llAQtlk">MIT License</a> for the <a href="/facts/Software_framework/EWasA8sG">software framework</a> part (the <a href="/facts/Library_(computing)/xRzL3P7q">library</a>) and AGPL for the compiler, so that applications written in Opa can be released under any <a href="/facts/Software_license/7enfIqhL">software license</a>, <a href="/facts/Proprietary_software/9zcskxYL">proprietary</a> or <a href="/facts/Open_source/7X9rCdz4">open source</a>. </p>