The full version is easily enough purchased through the Symantec online store (go to
http://www.ghost.com and the "Buy Now" link on the bottom left) or through resellers such as CDW.
Ghost Solution Suite 2.5 is perfectly capable of restoring to dissimilar hardware, as it includes a feature called "DeployAnywhere" which can inject mass-storage and network drivers after the image has been deployed (it can't do other driver types such as display or USB drivers in the GSS 2.5 edition, but that's less significant that having a restored result that boots, which is the primary thing we aim to take care of). You can run DeployAnywhere standalone (as covered in section 8 of the Implementation Guide) but through the console it's simply a matter of ticking a tickbox when creating a Task to restore an image to a client, which will manage the running of DeployAnywhere to retarget the image after it is deployed.
To restore the images you have already, you need to a) define an "Image" object in the console (under "Configuration Resources") to refer to the existing .GHO images, and then b) define a Task which contains a "Clone" type of step, and use that image definition as part of it - in real managed use, such tasks typically also contain "Configuration" task stages to then customize the newly-deployed image by renaming the machine and things of that nature.
Gathering inventory information is not Windows edition-specific; if you employ a "Refresh Inventory" task on a client machine, the inventory information is gathered the same way regardless of Windows edition. After information is gathered by running such a task against a machine, everything else is done by (user-modifiable) queries on that data, which comes originally from the Windows WMI system on the client machine and is then stored for querying against in the GSS console's database.
Windows Server 2003 isn't a part of the predefined inventory filters simply because there's little call for it - Windows 2003 is largely just a Server edition of Windows XP, but the base OS not significantly different from XP (as evidenced by the non-server edition of Windows 2003 64-bit being called Windows XP 64-bit) and the majority of our customers use the GSS console primarily to deal with workstation editions of Windows rather than server editions. Bear in mind that the "Dynamic Machine Groups" section is based on the Inventory filters, and it's possible to write your own filters and thus create customized folder arrangements based on all kinds of criteria based on the inventory information that the console gathers.