Copyright and software licences
Who owns software?
- When someone writes software, the law says how others may use it.
- Copyright protects the work; a licence grants permission to use it.
- Different licences suit different goals — revenue, reach, or community.
Copyright
- Copyright is the creator's legal right to control how a work is copied, distributed, modified and performed.
- It applies automatically (no registration) to source code, software, documents, images, audio and video.
- It encourages software: developers can earn from their work and re-use happens on their terms.
- It lasts a long time (often 70 years after the creator's death). General ideas and algorithms aren't covered by copyright — they may be covered by a patent.
Which is true of copyright?
Copyright is automatic on original works (including code) and lets the creator control copying, distribution and modification.
A general idea or algorithm is NOT covered by copyright, but may be protected by a:
Copyright protects the specific expression (the code/text); ideas and inventions may be protected by a patent.
Software licence types
| Type | Cost | Source given? | Redistribute? | Modify? |
|---|---|---|---|---|
| Commercial (proprietary) | Paid | No | No | No |
| Open-source | Free | Yes | Yes | Often, with conditions |
| Freeware | Free | No | Yes | No |
| Shareware | Free trial, then paid | No | Sometimes | No |
- Open-source splits into permissive (MIT, BSD — almost any use) and copyleft (GPL — modified versions must use the same licence, "share-alike").
Open-source software means:
Open-source publishes the source so the community can read, modify and redistribute it (under the licence terms).
A copyleft licence such as the GPL requires that:
Copyleft ("share-alike") forces derivative works to keep the same open licence; permissive licences (MIT/BSD) do not.
How does shareware differ from freeware?
Freeware is free with no source; shareware is free only for a trial, then requires payment.
Match each licence type to its key feature.
Commercial = paid/closed; open-source = source available and modifiable; freeware = free but closed.
Choosing a licence
- Link the choice to the developer's goal:
- commercial → earn revenue per user and keep control of the code;
- open-source → maximum reach and community improvement;
- freeware/shareware → free distribution, perhaps to upsell a paid version.
You've got it
- copyright is automatic and controls copying/distributing/modifying; ideas/algorithms → patent
- commercial (paid, closed) · open-source (source public, modify/share)
- copyleft (GPL) = modified versions must stay under the same licence; permissive (MIT) = almost anything
- freeware (free, no source) vs shareware (free trial, then pay)