Lightspark

Lightspark is a free and open-source Adobe Flash (SWF) player released under the terms of the GNU Lesser General Public License version 3.

WWW Official Site

Features

Lightspark supports most of ActionScript 3.0 and has an NPAPI plug-in. Though it has some support for it, it will fall back on Gnash, a free SWF player, on ActionScript 1.0 and 2.0 code.
Lightspark supports OpenGL-based rendering and uses OpenGL shaders. The player is compatible with H.264 Flash Videos such as those on YouTube.

Portability

The Lightspark player is completely portable. It has been successfully built on Ubuntu 11.04 on PowerPC, x86, ARM and AMD64 architectures. Lightspark has a Win32 branch for Microsoft Visual Studio and introduced a Mozilla-compatible plug-in for Windows in version 0.5.3.