I've mailed naTmeg already about agreeing on MIME type for MorphUp packages (my proposal is 'application/x-morphup'), so we can arrange browsers (after adding some functionality to MUClient) in such a way that click on *.pmi link will start MUClient automatically and add the new source. Of course there is some problem, you have to be an administrator of a web server to effectively add a new MIME type (which is the case for me ).