SilverFast is developed specifically for each command set and chipset of a given scanner model range in order to achieve our goal optimal scanning results. Thus you cannot use a SilverFast Version developed for one scanner for a different one, even if the scanners in question come from the same manufacturer.
If you want to use two (or more) scanners you would be required to have a licenses of SilverFast for each supported scanner. Once you have the first license (either bundled or purchased), you are eligible for a discount off further licenses of SilverFast. These would be considered "Additional Licenses".
On our online store, https://www.silverfast.com/buyonline/en.html?productline=scanner&filter=no, select the scanner you wish to purchase for, select your operating system and in the "License Type" select "Additional License". Under the "Existing software", select either "SilverFast 9" if you have a current SilverFast 9 license for your first scanner, or "SilverFast 8 or older" if your current license is SilverFast 6, 6.5 or 8. If you are selecting "SilverFast 8 or older" as the existing software, you will need to select the scanner manufacture and model of the scanner you are using for discount, and enter the SilverFast serial number. Once verified, you will see the discounted pricing.
If you are using a license from SilverFast 9, you will be required to sign in with your MySilverFast account information (email address and password).
Additional License from SilverFast 8 or older:
Additional License from SilverFast 9: