If it is in an EXPERIMENTAL Aircraft and in the U.S., you can operate it "On Condition" until it falls off the engine mount.
Be diligent with your100hr inspections.  NO Hand Waving!

The 9-series engines were used in US Predator Drones.  The US military worked with Rotax to improve quality and reliability.  Many engines were tested for thousands of hours with no internal component failures or replacement.  For experimental use, I would operate on condition inspection well beyond recommended TBO.  Also, be aware… depending on year and S/N, you may have engine with TBO less than 2000 TBO.

As per Bill's advice - in Australia aircraft not used for commercial purposes (hire, training, etc) can and do continue past TBO "on condition". 

A great many Rotax 9's go past calendar TBO many many years before they get to Hobbs (operating hrs) TBO. 

Each country is different with some of their rules and some are the same. You have to research where you live and their regulations.

I now have several friends with 3K - 4K hours on the engines and have heard of many others. They're all on condition. You don't have to be experimental in the US and even if your a SLSA.  FAA says with two legal documents (from 2011 & 2013) you can go on condition. Read the FAR's down to the very last sentence about TBO.

"You are allowed to use a program approved by the regulator authority)

(2013 FAA legal dept)

The rules applicable to the performance of maintenance, preventive maintenance, rebuilding,

and alteration ofS-LSA are contained in part 43 of Title 14, Code of Federal Regulations

(14 CFR). Section 43.13 sets forth the performance rules applicable to persons performing

work on these aircraft. Paragraph (a) of that section specifically states that:

Each person performing maintenance, alteration, or preventive maintenance on

an aircraft, engine, propeller, or appliance shall use the methods, techniques,

and practices prescribed in the current manufacturer's maintenance manual or

Instructions for Continued Airworthiness prepared by its manufacturer, or

other methods, techniques, and practices acceptable to the Administrator,

except as noted in § 43.16. I

Part 43 does not mandate that a person specifically perform maintenance, alteration,

or preventive maintenance solely in accordance with those instructions specified in a

manufacturer's maintenance manual. It also permits a person to perform such work in

accordance with other methods, techniques, and practices acceptable to the

Administrator.

Read attached file from the FAA