I'm no expert on the code, the licensing, or where the code originated, but having included features like (for example,) Bip85 (deterministic seed phrases that are backed up by the primary seed, which is a pretty slick feature,) could justify changing the licensing due to those features. If nvK wants to protect his intellectual property by protecting unique snippets, I don't see a problem with it as long as it's available to the public for scrutiny.
I understand the reasoning of both camps. Those who say it's unethical to use open-source code to inspire you to build your own software, only to prevent others from doing the same and using your code in their products are right. It is. But if his product is superior in any ways, or he thinks it is, I understand why he would want to protect it. Business is cold, emotionless, and sometimes doesn't know logic and reasoning. If someone feels there is a breach of licensing agreements, sue him. Can it even be done?