Software Licences

Software is a unique product. It can be very expensive to make the first copy of a programme, but it is cheap and easy to make subsequent copies. This be it very difficult to make a business out of selling software. The licence is a critical legal instrument in this.

Generally, you don't actually buy software, you just buy a licence or a right to use it. Almost all software is covered by a licence.

A software licence can be;

• Open source - where the user has access to the source code.
• Closed source or proprietary - where the source code is not available to the user.

There are various ways to implement either of these.

• Commercial - user pays for a licence to use the software
• Shareware - a free trial period is allowed, after which you pay
• Freeware - you don't pay for the software (eg free download)
• Anything else the author can dream up.

EULA

Microsoft uses the End User Licence Agreement with its products. This can vary between products, (eg Windows95 vs WinNT). Generally, it means you have the right to use the software on one machine, but denies you the right to share the software or to modify it.
The older licences allowed you to sell the software once, but current licences require an activiation key tied to your hardware. Apparently this restricts your rights to move the software to another PC, or to sell it. Microsoft say they are moving to a service model, which could mean the licence is only valid for a set time, say 2 or 3 years.
The EULA may give Microsoft other rights, eg the right to inspect your PC via the internet and alter software without telling you.

GPL

The General Public Licence was produced by the Free Software Foundation back in the 1980s. Their aim was to guarantee your freedom to share and change the software, and to ensure this freedom persists for all future users.
Under the GPL, you get both the source and binary code. You can modify the programme if you wish. You can sell or give away copies of the software, modified or not, but only under the GPL licence. This means you have to make the source code available to anyone who asks for it.
This is referred to as free software, in the sense of free speach, not free beer. It is also termed Open Source.

BSD

The BSD licence oginates from the University of California campuses at Berkley and San Diego. It was developed to cover software produced on campus, but can be applied to software developed elsewhere.
BSD differs from GPL in that you can redistribute software, but you don't have to provide source code.