If there is an OOB editor it has not been released.
However the OOB files are simply text files and most of the information on them has been known for some time.
All it takes to modify an OOB file is a simple text editor, you could use Notepad although I use an old version of Textpad.
I collected all the info on the OOB files I could find and made it available at the Engineering Department
http://acwgc-engineering.com/I understand there have been some changes to the Weapons list that I have not yet updated, I need to contact Rich about that.
The biggest problem with modifying an OOB was making sure to keep the proper use of Begin and End statements and using the correct symbols for the entries.
One thing that even some of the designers failed to watch was the 19 character limit to the name field, this is why some unit names look strange.
Once the OOB and MAP files were locked with Corinth 1.02 this was pretty much useless as you could load a modified OOB into the Editor but not into the game.
It was later discovered that you could modify an OOB file provided you kept the checksum the same, this was too much work for most of us so it wasn't used.
With the release of the Gold updates the OOB files were unlocked and modified files can now be loaded into the game.
I believe The Big Ten and Clash of Titans Tournaments are a direct result of this ability.