I don't think anybody's been able to provide a nulled version of OxyNinja Core (or Woo, for that matter.) The Ninja team has it locked-down pretty good (I guess.) But, it is a cool one to have.
At $119 USD it's a bit pricey, but there are some sellers on this forum that will install it for you on one of your sites for around $10. Once you have it installed on one site you can then bring in all the pre-made sections/headers/etc. Then, you can bring them into other sites by either copy/pasting these sections directly into another site using something like Hydrogen Pack.
Oxygen also provides a couple of different ways you can export/import these sections (as blocks) or pasting shortcodes. You can even export all the styles and selectors from the Ninja site into your other non-ninja sites and then have full access to all the utility-classes that Ninja Core has.
I found that it can be tricky to copy and paste these Ninja sections into a new site simply because you think you're copying the whole section/module but you're actually missing the parent container and so you notice that things don't necessarily look exactly the same.
It was frustrating until I figured out the reason why (when you're hovering over the section and then click "copy" (and you think you're grabbing the whole thing,) but you're not able to grab the Parent container, this has to do with the way these right-click (copy/pastes) plugins work.