What an option buys
An option is a promise to keep an offer open for a stated period in exchange for consideration. That consideration is what makes the difference: during the option period the optionor may not revoke, while the optionee holds a right, not a duty, to buy.
A developer pays an owner $2,000 for a six-month option. The owner is bound for six months; the developer may walk away and lose the $2,000, because option consideration is normally nonrefundable. This is not a bilateral purchase contract obliging both to close — that arises only when the option is exercised. The developer cannot demand the $2,000 back, and the owner cannot sell to a better-priced buyer without breaching the promise the $2,000 purchased.
The Due Diligence Period is an option
Georgia rule. GAR F201 paragraph B.8.d(1) states that including a Due Diligence Period makes the agreement, during its term, an option contract in which the buyer has paid separate valuable consideration of $10 for the granting of the option.
The contract is not suspended pending an inspection report — it remains binding. It is not "voidable by either party": only the buyer may terminate under the due diligence right. And the as-is rule applies unless the property is sold subject to a Due Diligence Period.
Assignment versus novation
A novation substitutes a new party for an existing one by agreement of all parties and releases the original party. O.C.G.A. 13-4-5 confirms that introducing new parties so as to change the person to whom the obligation is due ends the original contract.
The tempting wrong answer is assignment. In an assignment the assignor remains liable and the other party's consent is not necessarily obtained. Where everyone signed a release, it is a novation. Accord and satisfaction means satisfying an existing obligation by a later executed agreement, and mutual departure under O.C.G.A. 13-4-4 describes performance drifting from the written terms — neither substitutes a party.