This is a common question, so I'll attempt to explain:

Originally, I wanted to help the UKMP project, but as I got into it, I realized that UKMP's code is too messy to service. The entire application is crammed into a single massive file, among other things. In addition, UKMP's author didn't want to move to python 2.5 and sqlite3 for a database backend. I believe that step is necessary for good performance and clean code.

Therefore, Kagu is a complete rewrite of UKMP from the ground up with a clean, highly object oriented, design. It isn't perfect, and we're still playing catch-up to UKMP's feature set (though we already have a number of features that UKMP lacks), but we think Kagu is a lot easier to maintain and extend than UKMP.

Both projects are GPL, so UKMP is free to take from Kagu any code that it finds useful. (In particular, I think UKMP's author might like the Screen/Battery awareness code, and maybe the OSSOPlayer code, as we found GStreamer less than reliable) We've already taken a ton of code from UKMP and rewritten it for Kagu's object model. So it's not like the two projects can't benefit each other. This is, after all, open source.

Of course, if UKMP's author wants to join the Kagu project, we'll welcome him. We're always looking for new programmers to help out.