Drupal + Feeds for MRSS [developer/installer notes]:

The complete transmission.cc code can be found at:
  git://git.iskra.net/drupal/projects/tx
This is a git repository with submodules [
http://git-scm.com/book/th/Git-Tools-Submodules ]. If you're on the command line to get the rest of the code you then type (in the git repository you just pulled):
  $ git submodule init
  $ git submodule update
If you're using your favourite gui there should be a way of getting all the submodules.

All the code is standard Drupal and contrib with a couple of important additions.

The feeds are pulled with the http://drupal.org/project/feeds module. It uses the simplepie variant; and then uses an extention module to read the MRSS. This module is checked out as a submodule but is also now in a sandbox on drupal.org https://drupal.org/sandbox/ekes/1867408

In the transmission.cc site there are two content types for feeds: 'MRSS feed' and  'Video'. Posting a new 'MRSS feed' with the URL of the RSS feed adds that to the list of feeds that are pulled. Items in the feed are created as 'Video' nodes.

The node types, and the feeds settings to use them, and to map which parts of a feed item to which parts of the node, are stored in a 'feature' [this is a way of storing settings in Drupal, the main module is http://drupal.org/project/features ]. The relevant feature for this is the one found in 'tx/modules/features/mrss_feeds'

To make the site itself output MRSS in the RSS feed there is another module, again included but now also in a sandbox