Multiple choiceQuestion 1 · Recall
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By the end you can name the main types of software licence, say what each one allows, and justify which licence suits a given situation using cost, number of users, access to source code and the need to modify or redistribute.
When you pay for software you normally buy a licence to use it, not the software itself. The copyright owner keeps the rights; the licence sets out what you may do.
Two shops can sell the same program on completely different terms: one allows installation on a single laptop, the other on every machine in a company. The difference is the licence.
Reading the licence answers four practical questions:
Software licence
A legal agreement that states what a user may and may not do with a piece of software — for example how many devices it may be installed on, whether the source code may be modified, and whether copies may be redistributed.
Proprietary software is sold by a company that keeps the source code private. The licence is priced by how the software will be used.
| Licence type | What it allows | Typical use |
|---|---|---|
| single-user | one user, often one device | a student buying an office suite |
| per-seat / multi-user | a fixed number of named users or devices | a small office with 12 staff |
| site licence | unlimited installations on machines at one site or in one organisation | a school with 500 computers |
| volume licence | a discounted bulk agreement for many machines, often with a management console | a company rolling out software to 2,000 laptops |
| subscription | use for as long as payments continue; software may stop working if they stop | monthly accounting software in the cloud |
The advantages are support, updates and training from the vendor. The disadvantages are cost, no access to the source code, and the inability to adapt the software to your own needs.
Open-source software is supplied with its source code, and the licence allows you to use, study, modify and redistribute it — on conditions. The conditions are what distinguish the licences from each other.
| Licence family | Key condition | Consequence |
|---|---|---|
| permissive (MIT, BSD, Apache) | keep the copyright notice; often no other condition | you may use the code in closed-source commercial products |
| copyleft (GPL) | if you distribute a modified version, you must release your source under the same licence | good for shared projects, a problem for a company that wants to keep its code secret |
Open source is not automatically "no cost": a company may charge for support, hosting or customisation, and some open-source components have commercial support contracts. It is also not "no rules": ignoring the conditions is a copyright infringement.
| Term | Meaning | Source code? | Payment? |
|---|---|---|---|
| freeware | free to use, but the author keeps the rights | usually not available | none |
| shareware | try it free for a trial period, then pay to continue | usually not available | after the trial |
| public domain / CC0 | the author has given up the rights | often available | none, and no conditions |
Freeware is the one students most often confuse with open source. A free PDF reader is freeware: it costs nothing, but you still cannot see or change its code.
When a question asks you to justify a licence, work through these in order and say which one decides the answer:
A justification always links the licence to the situation: "a site licence, because the school needs it on 500 machines and a single-user licence would be more expensive and harder to manage".
Worked example: Worked example: choosing for a school
A school has 480 computers used by students, a small budget, and no programmers on staff. It needs an office suite on every machine. Which licence should it choose, and why?
Worked example: Worked example: choosing for a start-up
A start-up is building a paid app. It wants to use an existing open-source library for image processing and to keep its own source code private. Which licence family should it look for, and why?