Two things:
1. IMO sup (http://supmua.org/) is more mature and does about the same. However it's interface is a curses based one which is a plus and a minus.
2. Why not use an existing search products (like xapian)?
Mostly, the reason we do things the way we do, is because one of our primary goals is to make an end-user desktop app. Packaging is therefore a significant task and minimizing dependencies will help a lot.
We still have quite a bit of work to do on our website and message.
One of the reasons I started lumail (http://lumail.org/) was because none of the existing console clients worked for me. Specifically sup will die importing my 2013-1994 = 19 year mail archive.
