The journeyman system is basically a location based non-compete agreement. It protects the competitive business advantage of the master and gives him the confidence to share knowledge without his apprentice eroding his profits
Discussion
How would a society enforcing idea-ownership solved this problem?
That's what the patent system does, it is meant to reward the creators with royalties or a temporary monopoly on production
Hmm, I believe patents aren’t used for trade secrets like the above example for exactly that reason. They are only used when there is a likelihood that people are going to figure it out the secret in the process of making money on it. If obfuscation is possible, it works better than patents.