We have been looking to add SMIL support for GStreamer and GNOME for a while now. Problem have been that there hasn't really been and complete usable implementation yet under an acceptable license. Well I discovered Ambulant recently. Currently its under a GPL+exception license, but they seemed open to dual license it under the LGPL which would make things easier to relate to in a GStreamer and GNOME context.

Ambulant is a C++ based library which includes player(s) for a lot of platforms, including a simple Qt player for Linux. It currently use ffmpeg for network and format support and expat as its XML library. We would want to replace ffmpeg with GStreamer, expat with libxml and hook up Totem as the GUI. Currently fighting with its build system and some GCC4 issues, but hopefully I get it running to test it soon and then later on I hope someone who actually can hack is willing to help out to intergrate it with our stack.