In can only see two of these reasons.
The first one would be copyright issues, but as far as I know, Red and you are the only owners of the copyright on TMA's source code, so if both of you agree to release the code there isn't much of a problem.
The second would be that there are securities issue, so you'd rather do security by obscurity, which is fine on the short-term. If this is the case you could release non-critical parts of the site, and then possibly gradually release more stuff.
As for doing this for the future rewrite, that would also be great! But except if there are indeed security issues, it sounds like unnecessary tons of work.