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
Plaphoons v:974 Symbolic communicator, Communication board editor 22 21 12 Face-to-face communication software Windows Projecte Fressa Plaphoons interface image
Relumino Contrast and filtering 22 39 12 Special output software Android Samsung Electronics Relumino illustration
SignWriting Picture language 05 06 21 Assistive products for training in icons and symbols Center for Sutton Movement Writing SignWriting system of writing sign languages
SITPLUS v1.1.0 Cause-Effect Relation Learning 05 12 24 Assistive products for developing understanding of cause and effect Windows XP SP3, Windows Vista, Windows 7 CREA Sistemas Informáticos Sitplus interface image
SoundingBoard 4.0 Symbolic communicator 22 21 12 Face-to-face communication software iOS AbleNet SoundingBoard communicator image
Speech Assistant AAC (Android) 5.5.4 Text-based communicator app 22 21 12 Face-to-face communication software Android 5.0 (Lollipop) ASoft "Speech Assistant AAC" interface image
TapTapSee (Android) 3.1.0 Artificial vision 22 27 06 Indicators with acoustic signals Android 4.0 (Ice Cream Sandwich) CamFind Inc. TapTapSee interface image
TapTapSee (iOS) 3.1.0 Artificial vision 22 27 06 Indicators with acoustic signals iOS 7.0 CamFind Inc. TapTapSee interface image
WebbIE Web Browser 4.5.0 Web browser 22 33 15 Browser software and communication software Windows XP SP3, Windows Vista SP2, Windows 7, Windows 8 WebbIE WebbIE interface image
Widgit Go Lite 1.0 Symbolic communicator 22 21 12 Face-to-face communication software Android 3.0 (Honeycomb) Widgit Widgit Go communicator interface image