Download it here.
This is the final release of MacJournal 5.1. If you've been following the betas all along, not much will be new. But if you're coming from 5.0.4, there are some nice new things. I think the three biggest things are the "three-pane view", editable entry windows, and Karelia's Media Browser window. Let me know of any problems you find. I will update the in-application update mechanism soon as well if you just want to wait for that.
Note: If you saw it posted yesterday and downloaded it then, it may have been the incorrect build. A bad disk image was posted yesterday but has been corrected now. It was just beta 9, expiration date and all. Re-download using the link above to get the real 5.1.