Free of charge software

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Free software, freedom-respecting software, software libre, or libre software is computer software distributed under terms that allow users to run the software for any purpose as well as to study, change, and distribute the software and any adapted versions. The right to study and modify software entails access to its source code. For computer programs that are covered by copyright law, this is achieved with a software license by which the author grants users the aforementioned freedom. Software that is not covered by copyright law, such as software in the public domain, is free if the source code is in the public domain, or otherwise available without restrictions. Other legal and technical aspects, such as software patents and digital rights management may restrict users in exercising their rights, and thus prevent software from being free. Free software may be developed collaboratively by volunteer computer programmers or by corporations; as part of a commercial, for-profit activity or not.

Source: Wikipedia

List of free products
The table shows the products that are distributed for free The table shows the information distributed in seven columns: 1st name of the product; 2nd version of the software; 3rd type of product according to the TecnoAccessible classification; 4th classification of the product according to ISO 9999; 5th the operating system for which it is compatible; 6th company, person or entity that has developed the product; and 7th illustrative image of the program interface
Name Version Type ISO OS Maker
eSpeak 1.48.04 Text-to-speech 22 39 12 Special output software Linux, Mac OS X, Windows eSpeak project eSpeak interface image
Florence Virtual Keyboard Virtual keyboard 22 36 18 Input software Debian GNU/Linux, Ubuntu Ardesia project Florence Virtual Keyboard image
GoTalk NOW FREE 4.5.1 Symbolic communicator 22 21 12 Face-to-face communication software iOS Attainment Company GoTalk NOW communicator image
iDentifi 1.2.1 Artificial vision 22 27 06 Indicators with acoustic signals iOS 9.0 getiDentifi iDentifi interface image
It's Accessible (Android) 1.2.2 Resource Location 99 Unclassified Android 2.3 (Gingerbread) EsAccesible App It's Accessible interface image
It's Accessible (iOS) 1.2.1 Resource Location 99 Unclassified iOS 5.1 EsAccesible App It's Accessible interface image
Liblouis 2.6.3 Vision accessories 22 39 12 Special output software Liblouis project Architectural overview of Liblouis and Liblouisxml
MozBraille 0.1 Web browser 22 33 15 Browser software and communication software Linux, Windows Mozdev.org MozBraille screenshot image
NVDA 2017.3 Screen reader 22 39 12 Special output software Windows XP, Windows Vista, Windows 7, Windows 8, Windows 10 NV Access Voice Settings window image
Openclipart Picture language 05 06 21 Assistive products for training in icons and symbols, 22 21 12 Face-to-face communication software Open Clip Art Library Examples of clip art from the Openclipart