Six Apart own the one of the most popular Blog software, Movable Type.
The latest version is 4.1, which released on Jan 24, 2008
Now MovableType has three distributions under different license.
1) MTOS (Movable Type Open Source) is a distribution of MT available under the GPL (v2).
It is Open Source license. Free to download, use, and modify. The restriction is keep Open Source, if you want to re-distribute it.
2) Movable Type for Personal Use is a distribution of Movable Type that is 100% identical to MTOS from a code perspective, however it is only available under a proprietary (closed source) license.
This is a free version for personal use. I also use this distribution.
3) Movable Type for Commercial Use is a distribution of Movable Type that includes the commercially-licensed equivalent of the core open source product and includes the Movable Type Professional Pack that contains features exclusive to our paid customers.
The advantage is the Professional Pack. The features are not included into the MTOS and personal license.
There is also one news from my friend. He made a Chinese (simplify) Language pack. It works on MTOS and MovableType Personal. You can download it here.