Software developers are fully capable of writing good quality software without a need for licensing, but managers and product people come in the way. If I had to write 5x tests covering every branch, my software would never complete.

What I suggest considering instead of licensing is a voluntary GAP (good authorship practices) certification for a project, unique to each approved programming language, comparable to GMP (good manufacturing practices) in the pharmaceutical and food processing industries. Customers should then develop a culture of licensing commercial software only if it has this certification. As for who will certify, on what basis, at what cost, and how will it keep up with changes in the real world, all of these are good questions.