Here are a few options for a formal rewrite, depending on the desired emphasis:
Option 1 (Direct and Neutral):
Developer of Fox River Resort Refutes Allegations of Muslim-Exclusive Policy
Option 2 (Formal and Authoritative):
Fox River Resort Developer Dismisses Claims of “Muslim-Only” Facility as False
Option 3 (Concise):
Developer Denies Speculation Regarding Religious Exclusivity at Fox River Resort
Recommendation: Option 1 is the most professional and standard journalistic choice.