Once you have a property under contract, you have equitable interest, and at least in my state, that provides you the legal right to market the property, regardless of whether you have a license or not.
Plus, once you have the property under contract, you're not marketing the property on behalf of the seller (which WOULD require a license); instead you're marketing your interest in the property on behalf of yourself, which I would be surprised to find is illegal.
That much is correct. You can market your equitable interest in the property and sell (assign) the contract to a 3rd party, providing the contract does not say otherwise.
All contracts, except personal services contracts, are assignable unless they specifically state otherwise. If you assign a contract, your liability to perform remains with you and your assignee, unless the contract specifically states that you are released from liability upon assignment.
What I'm saying is that the language in the contract about "buyer" and "seller" implies a duty to perform as such. If you include a clause or a contingency that is external to that duty, then it changes the nature of the contract into a listing agreement.
A contingency or provision that relieves the buyer from the duty to perform as a buyer and substitutes a duty to perform as if he were a broker will change the nature of the contract into a listing agreement. If you're not licensed or don't have limited power of attorney, then you're breaking the licensure laws.
Just because the title of the contract says "Purchase and Sale Agreement" doesn't mean that it is a PSA. The nature of the duties specified within the contract determine what kind of contract it is.
It really doesn't matter what a few attorneys may say in advocating their client's position. What matters is that contract law is what it is. If you have no duty to perform as a buyer, then your duty is to perform as a broker. That's why providing earnest money deposit as fully liquidated damages for breaching your duty as a buyer is required. If you use an "inspection clause" to bail out and get back your EM, then you must have found something in the inspection that you don't like. You must have a valid basis for exercising the contingency clause.
That's why I use "sole subjective discretion" in the inspection clause, so they can't argue with me that I don't like the available property insurance quote or I don't like the shape or size of the lot. It's not subject to further negotiation; the deal is dead for a valid inspection reason and I get back my EM.
Your contingency clauses must be based on material issues with the property or your own capacity to perform your duty as a buyer (subject to your subjective opinion). You cannot change your duty to perform as a buyer into a duty to perform as broker, unless you have proper legal credentials.
By the way, as an optionee in an option contract, you do not have an equitable interest in the property. You only purchased the unilateral right and option to buy the property for a set price for a set price. You're not obligated to buy the property, therefore there is no equitable interest conveyed by the option contract. To get that equitable interest, you must exercise the option and sign the attached purchase & sale agreement to create a bilateral obligation.