Google or Facebook would not be global leaders without the global standards of HTTP, Email, Hyperlinks, Unicode, JavaScript, HTML, and many other technologies. After all these successes it should be obvious that being secret or proprietary isn’t always smart. Only certain kinds of projects should be kept proprietary:

Your secret sauce. The magic elements that would reduce your competitive advantage by more than the savings and reach of open community development.

Information that, if disclosed, would cause more harm than the good open sourcing brings. Some source code contains trade secrets or information under NDA that cannot be disclosed. Happily, these typically can be excluded from open source distribution by simple refactoring, at some additional cost. Other source code may open the doors to a possible copyright or patent lawsuit or PR gaffes. (Oh my, the things some programmers type into the comment fields!) You’ll need to review every line of code, which unless you already do code reviews, has a cost . (And the benefit of a long overdue code review!) Additional refactoring may be necessary to minimize potential legal entanglements.

Lesser value projects that aren’t worth the trouble of converting to open source. No one wants to waste resources or reduce their ROI by staying proprietary unnecessarily. Unfortunately, very little of your (non-commercial) software has any value to anyone else. If you put it on GitHub as open source, no one would show up to offer free help. Few enterprises bother opening their source code because they have nothing (non-commercial) worth open sourcing.

Thankfully ATF had been code reviewed, copyright reviewed, patent reviewed, and refactored. It wasn’t secret sauce. It did have substantial value to other tools programmers (and it doesn’t have any obvious open source competitors). Happily it immediately perked interest (#1 on reddit upon release) and our community is growing day by day.