Rule 3: open source first. Before you build something, look for a tool that already does the job.
Open source software is software whose code you may read, change and run under a public licence. A licence is the legal paper that says what you may do with the code.
Why
- Speed. A mature tool is months or years of work you do not repeat.
- Quality. Many users have found the bugs. Many people have read the code.
- Cost over time. Code you write is code you must maintain for ever. We call this tech debt: a promise of future work.
Free is not the same as cheap. Every tool has three risks:
- Licence. Can you legally use it the way you plan?
- Health. Will it still be alive next year?
- Fit. Does it do what your customer needs?
The four rungs
Start at the top. Go down only when the rung above fails, and write down why.
| Rung | When | What you do |
|---|---|---|
| Search | Always, first | Look for open source with an acceptable licence |
| Use as is | It meets every must-have need and the licence passes | Configure it. Do not change its code. |
| Adopt and patch | It meets most needs and the gaps are small | Use it with a small, tracked set of your own changes |
| Build | Nothing fits | Build it, and write down that you accept the full tech debt |
The full method is in The OSS-first ladder.
Two warnings
- No licence means no permission. Code on a public site with no licence file is not open source. The author keeps all rights.
- Open source is not always safe. Some licences limit commercial use or require you to share your own code. Read before you adopt.
Write it down
Every choice gets a short decision record. It says what you needed, what you compared, what you chose and how you could leave. A template is in Decision record.
Key points
- Search before you build.
- Check the licence, health and fit.
- Record the decision in git.
