The status of this project is: STABLE. I do not foresee any incompatible changes to the API and will call it 1.0 soon.
To get the code:
hg clone http://hg.red-bean.com/lastfmsubmitd/
To download in package form:
lastfmsubmitd is a daemon meant to be used by Last.fm player plugins. It handles all aspects of submitting data to the Last.fm servers, so that player plugins only need to watch what songs are played and write a representation of each played song to its spool.
The format used for serializing songs is a simple YAML dictionary, which can be constructed with YAML libraries (available for many languages), or printed ad hoc. The spool is managed with standard unix permissions, and many different players can use the same daemon to submit. Each instance of lastfmsubmitd uses a single account.
The format used by lastfmsubmitd is also used by Ears, my collection of other MusicBrainz and MPD clients. You may be looking for the program lastmp, which used to be distributed as an example with this package; it has been moved there.