Okay let me go through each one
1) Do you have a multiple site discount for purchasing more than one?
Yes you can email firstname.lastname@example.org
with how many sites we are talking about and they can give you a quote. The discount varies by the number of licenses purchased.
2) I like the integration with the registered user database swet up with VB3. Will this use the same skins that are already present on the rest of the vbulletin site and a cpms portal page?
The user's stylesheet selection in vbulletin can be used in Photopost and will change when they change styles.
3) For user uploads, can these be set to where an administrator has to approve each image before it will actually be shown publicly? Im worried about people just registering for the forum and posting images and galleries not related to the site.
Yes there is moderation per usergroup so if you do not want images or comments showing before you approve them this is standard.
4) One of the largest features we have on our site is a monthly vote, sort of an 'image of the month'. Does this support any voting or polls based on images in a particular gallery?? IE: Create a monthly gallery of images, registered members can vote. Also, is there a way to 'hide' the results until a particular time so that no one knows the results until an admin decides to show them?
Yes you can choose in category editor regular ratings or contest. if contest is selected admin can elect when to start and stop it. Once a member votes they can see the count much like a poll in vbulletin.
5) On some sites I see a lot of superflous information posted with each image, can this be edited to one or two simple lines, such as title of the image/gallery, and the member who submitted it?
You can control which items like description title comments filesize etc is displayed under the photo and thumbnails
6) Can the number of rows and columns of thumbnails for images and galleries per page be determined by the site administration?
Yes you can define how many columns for thumbnails and how many features to display.
7) Watermarks, can this automatically watermark each image in the albums?
Yes you can setup selective watermarking per group so it can be everyone or just one group. You can also choose between onthefly watermarks and permanent watermarks.
8) Does this package have the ability to limit hotlinking images in the gallery from outside pages? Secondly, if hotlinking is allowed, would it be possible to have it watermark the hotlinked images as well?
You have the ability to move the large images outside the webroot or a secondary location and also there is an htaccess editor in admin where you can write your own code to block them from being hotlinked. You can not watermark hotlinked images.