Can you explain open-source in one sentence?

I’ve been working in open-source for about a decade now. For example, I have contributed code under an open-source license, I have run a project, and — though this is probably unusual — I have caused my employer to draft its first open-source license so I could contribute the code and run the project.

I think I’ve learned a little bit about open-source and so ask others who have worked in the open-source and free software communities the following question:

If you had to summarize what you have learned in one sentence then what would you say?

Here is my answer:

You must be completely open — holding nothing back — for if you hold anything back then you will lose trust, and trust once lost is almost impossible to regain.

What’s your answer?