If the code were kept secret, or if you could prevent such use with DRM, copyright law would be irrelevant. By having the code in the open, you don't 'implicit

If the code were kept secret, or if you could prevent such use with DRM, copyright law would be irrelevant. By having the code in the open, you don't 'implicitly allow' unlicensed uses -- you just become reliant on copyright law as your protection.