Why it's time to stop using open source licences

> How about no licence at all – that is, putting software into the public domain?

First, that's not "no license at all" -- a public domain release identifies the copyright holder of the released code, and people don't have unlimited rights to public domain code. There are still license terms at work.

Second, this scheme would allow people to incorporate public domain code into their projects without sharing their derived version -- meaning it privatizes public code and would increase the percentage of code that's proprietary and inaccessible.

The advantage of open source licenses is that it requires those who use open-source code to open their source as well. Public domain "licenses" eliminate this requirement.