Only trusted programmers will be allowed to make changes to the project.
Explanation:
Let us understand first what a "closed source project is". It is quiet opposite to open source. What an open source will have?
- FOSS -Free and open source
- Source will be available to everybody
- User can make changes to the existing code and even release new software
- He can make changes in the software for his own personal use too
- There will be community to collaborate
So all the above will not be there for "Closed source". So the code is not free and it is confidential. Only trusted programmers can work on it.