Unknow Compression Algorithm

Hi all, this is my first topic.
I'm trying to understand a compression algorithm used by a games maker, preface they themselves have released a small program to unzip their files for modding, then I suppose isn't illegal.
The two files for comparison were obtained from the original game (compressed), and from file uncompressed by the released program (is a exe).

Obviously is a proprietary program then the source code is not released, but certainly from a first analysis with a hex editor seems to be intuitive:
If you see the string "Scene Root" is rewritten equal, the string "bone_root" is written "bone_r" because i suppose "oot" string is already in the previous string. :***:

http://dl.dropbox.com/u/47659776/ballista_crank.zip

After this introduction someone can enlighten me ? I would be very grateful !
The purpose of this is just to understand if the same method was used to compress an animations used by the game in some special cases, however, is already dated and now unpacked to 99% with programs made by its to support modding, butt this aspect have been neglected and no longer offer support for this game.

Thanks.