Has Northrop Grumman thought about marketing the YF-23 for Export? There are a lot of Nations that want a Gen 5 fighter.?

NG has to get government clearance to sell the YF-23 to any country.

They are not allowed.

The ATF program was essentially financed by the government, who therefore owns all the design rights and prototypes, so it is not up to Northrop Gumman to decide if they can do something, but up to the US government to allow it.

First, if a US made weapon system is not used by the US military, no other country wants it. Northrop learned that lesson the hard way when it tried to market the F-20 Tigershark abroad after the US Air Force decided to buy upgraded F-16C/D instead of F-20.

Second, and most important, there was absolutely no way would the US Government allow transfer of YF-23's sensitive technology to a foreign nations, even its closest allies. In 2010 when the production of F-22 was about to end, Australia, Israel and Japan approached the US about buying some F-22s. Even though the 100-120 additional export aircraft would have extended the production run and reduced the per-aircraft cost, the US flatly refused, despite the fact that F-22's stealth, avionics and engine technology was more than 20 years old at that point and the same three countries were allowed to buy the later technology F-35. Israel was even permitted to plug and play its own apps on the F-35's mission computer to allow it to integrate its own weapons, sensors and countermeasures. It became the second nation behind the US with operational F-35 capability. The F-22 production ended in 2011 and the Government ordered Lockheed to destroy all the tooling used to build F-22s.

Today, both China and Russia are close to deploying their own fifth generation combat aircraft and Japan, South Korea and Turkey are starting to develop their own stealth fighters.

Of course they did. But the technology used in the YF-23 remains subject to the very same federal export restrictions which govern production of the aeroplane which beat it in evaluation tests, the F-22 Raptor which is shared between the USA and the UK.

Selling a bare airframe alone with engines would likely be difficult enough because of the secret stealth technology. But that wouldn't fly without the avionics packages which are subject to extremely stringent export controls which only allow the USAF and UK's RAF to operate them.

It hasn't been approved for export nor did it ever go through the necessary development to bring it to the point where it could be if the U.s. government okayed it. .

It is hard to sell a fighter aircraft manufactured by an American firm to foreign nations that is used by the US military. It is almost impossible to sell one that is not.

They are under contract with the US govt on what they can and can not sell to each country. Besides national security, the US paid Northrop some parts to develop those two prototype.