Yes. The open pilot warranty in english means:
Dear Mr. Insured,
If you let a pilot who meets the open pilot warranty fly your airplane, and he prangs it, we'll make YOU whole. If he doesn't meet the requirements, you are S-C-R-E-W-E-D.
Love,
Your Insurer
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Nothing in there says that the Pilot who isn't named is protected. Now, depending on their exposure and other factors they may choose not to recoup their loss, but don't count on it.
The only way to be protected by ANY insurance policy is to be NAMED as an INSURED on that policy. A waiver of subrogation is just an agreement by the insurer not to sue you to recoup their loss, it does NOT extend protection.
Example: You rent a plane (a recent airplane like a C172S or DA40) from FlyRight FBO, who has a 1000.00 deductible and a wavier of subrogation. You, through ordinary negligence, land the airplane in a farmers field, hitting a prize bull. You have no insurance coverage of your own.
The airplane needs $40,000 worth of goods and services to get it back to it's previous condition and ready for rental again.
The farmer want's $250K for his bull.
The farmer sues you (as the pilot), FlyRight, the manufacturer, and everybody else he can think of.
FlyRight's insurance fixes the airplane, and settles with the farmer to cover FlyRight's exposure as far as the bull goes. FlyRight collects $1000 from you and they are happy. The insurance does not sue you due to the waiver of subrogation.
The farmer is STILL suing you, and you have to defend that suit on your own nickle.