Which of the following is a violation of license law?

The violation of license law here pertains to the prohibition of discrimination in real estate practices. Encouraging a seller to reject an offer based on the buyer's religion is a clear violation of fair housing laws, which are designed to promote equal opportunity in housing. These laws prohibit discrimination based on religion, race, gender, and other protected characteristics. Real estate professionals are legally obligated to treat all potential buyers equitably and cannot influence a seller’s decision in a discriminatory manner.

While the other actions listed may present ethical concerns or violate other regulations, they do not directly fall under the same category of discrimination as specified in the law. Placing a "For Sale" sign with the seller's consent is standard practice, and advertising a prize without mentioning a timeshare presentation may be misleading but does not inherently involve discrimination. Thus, the focus on discrimination in the correct answer is what makes it a definitive violation of license law.