Your question covers many of common users interrogations, so I will try to reply as accurately as possible, point per point:
_ You can safely store your Analog Factory license on the Steinberg dongle. Steinberg, Arturia, Korg, IK Multimedia... whatever the brand, as far as the type is correct: Syncrosoft USB-eLicenser. Don't confuse with concurrent and incompatible protection devices as PACE Ilok, Nalpeiron, etc.
_ Functionally meaning, there is no need for a need; but this is undoubtedly a major comfort of use: instant restoration in case of computer heavy maintenance, and your synth can trun on several computers of your own (one at a time).
_ The USB-eLicenser will then perfectly suit your needs.
_ Syncrosoft is now part of "Steinberg Media Technologies GmbH", the website with useful programs and docs is now
http://www.elicenser.net. However I'm not sure you can buy from them directly. Rather address to your favorite local music shop (Steinerg of Korg dealer), or through our
online shop or any third-party online vendor; they often sell this device as "Steinberg Key".