Posting Data directly to the Form Action

[clickthru]

I've been asked if its possible to create a copy of this form:
http://www.regulations.gov/search/Regs/home.html#submitComment?R=0900006480b20b5f

for a political group that wants to host a copy of the form on their
site, and submit it to regulations.gov. Is it possible to post data to
a GXT form A) from a different domain and B) what format do I need to
post the data? JSON? What would the call look like? I'm assuming the
url of the submit action is regulations.gov/submitComment/ but what
would my call look like?