Is it possible to enable indicator/notification support for the LastFM client? Is there a plug-in or PPA for this? If not, is this support being worked on?
As an aside, is the LastFM client open-source... can the community work on this?
Unfortunately this is not possible at all. Additionally, if using the last.fm client with Unity you may experiences some oddities.
The last.fm client is open source and con be downloaded by running
Whether or not "the community" is wokring on addressing this depends on whether anyone is interested in addressing it. So, either encourage someone you know to work on it, grab the code yourself and work on it, or raise this issue on the last.fm support forum.