[Disasterpiece]

Well, this is what a quick reply form looks like:

Attachment 130860

You should be able to recognize what you will need to send.

The securitytoken will be a problem, you'll need to login, download the frontpage to get your generated securitytoken (it's in the html code in plaintext, so you just need some regex to grab it).
The login method is also a POST request to the login form. You'll need a securitytoken again, so this is a bit of code and tricks to get it working, but it's doable.

Another method would be to create some kind of API script on your server, which accepts all the necessary post data and inserts them into the database directly.
You'll need to have an idea of the internal vbulletin functions to create posts/threads OR you try to inject it directly with a mysql query.
Biggest problem will be to make the script secure, but then again you simply need to check the request IP for equality with the server ip running the mod.

Here are neat examples on how to use curl for simple GET/POST requests: http://de3.php.net/manual/en/functio...exec.php#98628