I've looked into this, and unfortunately according to ldd the plugin seems to be linked against a library called libFlashGraphics.so (recalling from memory) which is what heavily ties libflashplayer.so into WebOS's WebKit luna subsystem (closed libraries/apis) and is needed to display the flash content in the browser, so my assumption is that libflashplayer.so in WebOS is only processing the flash data, while libFlashGraphics.so is being used to actually display flash content from within WebOS's browser.

So i'm assuming that your best bet to getting WebOS's flash plugin working is to reverse engineer libFlasgGraphics.so to work with X11(WebOS uses DirectFB) and Microb.