Is registration required?
vDos is free for personal use. It will check if the PC is joined to a domain, or files on a network drive are accessed. Then the About popup is displayed every three hours of continuous use. So vDos is also commercial software for (supposed) nonpersonal/business use.
What will it bring?
That nag won't popup anymore. You would contribute to rewarding the countless hours invested in vDos, further development and support, keep vDos freeware for most? You'll be informed of new versions. Some two weeks after the initial release, so eventually reported bugs will be fixed. Registered users however generally don't care much about new versions. The current one obviously does the job… I could be more open to your specific issues or wishes, and supply an intermediate pre-release to address those.
What about new versions?
Registration is lifetime and valid for any version. If I would decide to change this policy, it won’t affect existing registrations. This is of course no sound business model, while licensing vDos will cease in time. vDos is however mostly a paid for hobby, so I can commit myself supporting it. As long Windows supports 32-bit applications on x86/64 based PC’s, vDos should just continue to work. Future support not mandatory per se. To be real safe, a 64-bit vDos is available for registered users. Mind, that has a larger footprint, runs slower and only on Windows 64-bit.
How to register?
Filling out the registration form and creditcard payment (powered by Stripe), you’ll receive an email with a license file and invoice. The license file is to be copied to the vDos directory. That’s it, no activation procedure or online validation are involved. Transferring a registered vDos to other/new systems still remains a mere copy of some files (plus one). vDos can be registered in two flavours, they only differ in what vDos eventually validates:
Username: € 50.
Based on the Windows username. You can opt for more than one, but the price is per username.

Network: € 250.
Unlimited users, as long the PC’s are joined to the registered domain or that network drive is addressed.
Money back guarantee?
No, you can (should) evaluate vDos for as long you need to be confident it fulfills your requirements. Once issued vDos licenses can’t be revoked (nor expire) since vDos is fully portable, w/o online validations.
The required username(s) or network ID are shown in the About popup, the vDos window System Menu - About, or issuing the ABOUT command at the vDos/DOS command prompt.

A network with upto 4 users, you would probably choose the Username option. 5 or more, certainly Network.