Getting form Array from a webform created with Webform module?
First off you'll need to know the form_id. You can get this a million ways but the 2 I use frequently are using the devel module that has the dpm() function to display any variable you want to the screen. So in a hook_form_alter you can put dpm($form_id) and get it that way. Another way is to just view the source and find the opening form tag. The id is in there as well.

Once you have the form id you can use drupal_get_form($form_id) to get the form array.