The base version for syntax analyzer is Delphi 7 source format. There will be other versions supporting in next releases, including Delphi2010

I finish comparing but structure tree does not contain all of program objects. Where they are?

You should know that only difference program objects will be shown in the syntax tree after comparing. But you can see any equal program objects, because they are always in the editor in collapsed form.

After comparing I see empty structure tree. Why? 

You  see empty structure tree, if both your files are equal.

I try compare 2 DFMs, but I can not understand the result

May be, you try compare BINARY  DFM files.  The utility requires  DFM in text format

What "syntax.ini" file for? May I change it and when I must do it?

This file is to set syntax- extension link. It has simple structure as:

For example, PASCAL section has 3 extensions by default  - "pas", "dpr" and "pp".  So, when CodeMerger loads any file with these extensions, it  "knows" that the file has *pascal* syntax.

Of cource, you may add any new extensions to this file.