This is a video result from Adobe Flash Player:
http://www.mediafire.com/?4jfu111z8azfcvk

You'll see that the animation (which is loaded from external SWF) plays.

This is a video result from Gnash:
http://www.mediafire.com/?uj7a5i7w909irk4

You'll see that the external SWF animation does not load.

Gnash's console output shows:

119 TRACE: loader: starting
120 ACTIONSCRIPT ERROR: Could not find target 1 (evaluated from [number:1])
120 TRACE: loader: failed to start animation loading

Test SWF, full source code, build scripts, screencasts, and logs (verbosity 2
with action error log) are attached.

Gnash: 0.8.11dev (git 15d61a8 26-Dec-2015)
Flash Player: 11.2 r202 (11.2.202.491) Standalone
System: Debian GNU/Linux 7.0 Wheezy i386

(file #35960)

I have created a test Flash file which tries to display an external SWF file,
by loading it to `_level1` using `MovieClipLoader.loadClip(URL,levelNumber)`:

var loader:MovieClipLoader;

trace("loader: starting");
loader = new MovieClipLoader();
if(!loader.loadClip("testanimation.swf", 1)) {
        trace("loader: failed to start animation loading");
}
-verbatim+

It works as expected under Flash Player, but failed under Gnash;
`MovieClipLoader.loadClip()` rejected `levelNumber` argument,
and returned `false`.

Gnash: 0.8.11dev (git 15d61a8 26-Dec-2015)
Flash Player: 11.2 r202 (11.2.202.491) Standalone
System: Debian GNU/Linux 7.0 Wheezy i386.

Note: If I replaced the `levelNumber` argument with a `MovieClip` instance,
it would work without problem under both Gnash and Flash Player.