Types of software licences
Introduction
Software that you can buy can have a number of different licences. These include open source software and proprietary software.
Open source software and the Open Source Initiative
When you buy a piece of software, you can run it and use it but you cannot see the code. That means that you cannot modify it and you are not allowed to distribute it to other people. There are, however, lots of software applications where you can do exactly that. You can download it and use it, distribute it to others and you can also see the code. That means that you can change it and generally play around with it and experiment. This is a great way to learn and improve your programming skills! Examples of open source software include a Virtual Learning Environment called Moodle and the operating system known as Linux. Open source software is promoted by an organisation called the Open Source Initiative. They actively support the development and distribution of open source software and its promotion and use.
Free Software Foundation, the General Public Licence (GPL) and copyleft
The Free Software Foundation is an organisation similar in purpose to the Open Source Initiative but set up about 10 years before the OSI. They also promote and support the idea of 'free software' i.e. software that can be created, used, distributed, studied and modified for 'free'. In English, 'free' can mean 'for no money' but it can also mean 'without any ties as in freedom'. The differences between the Free Software Foundation and the OSI are essentially tiny, coming down to the meaning and philosophy of the word 'free' that drives the promotion of this type of software; they are both organisations that have the same aims.
The most widely used licence for free software promoted by the Free Software Foundation is the General Public Licence, the GPL. It is also known as the GNU GPL licence. When someone writes some software that they are happy to release for free, they can release it with the GPL licence. This clearly let's people know that it is okay to use, distribute, study and modify the software for free. It someone does decide to modify and then distribute the software, because the original software came with a GPL (or GNU GPL) licence, part of the agreement of this licence is that modified copies that are distributed should retain the GPL licence. The requirement that modified and distributed copies of software retain the GNU licence is called 'copyleft' software. This is a play on software that is copyrighted.
Copyright
When a program is copyright-protected, it means that someone or some organisation owns the legal rights to the program. Copyright is the term used to describe any intellectual property (not just software but books, songs, drawings, poems, films etc) that has the protection of the law from being used without paying a fee if appropriate, copied, modified or distributed. Somebody who does any of these things with copyrighted software can be prosecuted.
Proprietary software
Many of the programs you use today are known as 'proprietary software'. With proprietary software, the owner has only given you permission to use it, usually (but not always) by selling you a copy for a fee. Windows, Serif applications and Microsoft Office are good examples. If you want to use any of these software titles, you must buy a copy. Once bought, you don't actually own the software (although you do have a copy of it) but you have bought the right to use it. You can't make copies of it and distribute them to friends because that breaks the licence agreement you made when you bought the software. You can't go and modify the code either. You have only bought the right to use it. This type of software is known as 'proprietary software'.
Shareware
Another common type of licence for some proprietary software is shareware. Software that comes with a shareware licence can be used and shared but comes with restrictions. This can include a time-limited right to use the software, limiting its use for personal not commercial use only and no rights to use the software for commercial gain e.g. by modifying or repackaging it and then selling it on to customers. This type of software is initially free although a fee is usually payable if you want to use it after a period of time, if you want to unlock certain features or remove advertising, for example. Shareware is essentially the same as a 'free trial' and is used by companies as a way of getting their software out to customers to try. It is often distributed with magazines or available as a download from a website.