I have a hacked up fork that provides only the functionality necessary to make this work with the systemd shipped on fedora-17. It does this by mostly just commenting out functions and definitions that are not present.
What are your thoughts on making this lib compatible with the various versions of systemd out in the wild? It might make the code a bit ugly but might be worthwhile. Not sure exactly how to approach this other than some autoconfig style checking for certain functions and wrapping things in #ifdef's.
I have also exposed sd_journal_get_fd() function because I want to get the file-descriptor to the journal.