Interesting paper. Actually it's not only the developers who are challenged. Even lawyers often have trouble understanding these licenses, because often formulations are used that are not written by lawyers and are not common. Moreover, final clarity on the exact interpretation and effect of these licences will only be achieved once there are judgments from the highest courts. And since every country has its own legal system and there are many different aspects to clarify, many such judgments are needed. So the matter is not so simple. Whether the developers understand the licenses or not is just one of many problems.