vDos is largely freeware, even open source. A small part of its proprietary code is however excluded from the source code packages (of no interest if you don’t plan to modify and rebuild vDos). vDos will check if the PC is joined to a domain, or a network drive is addressed. The About popup is then displayed at startup. That eventual popup can be clicked away, without consequences for vDos’ functionality. If vDos isn’t used that often, this shouldn’t pose a real obstacle. So vDos is also sort of mild nagware for some targeted business users. A registration or donation would of course still be appreciated, even if the popup/nag doesn’t apply.
That nag won't show up anymore. A good feeling you'll contribute to rewarding the countless hours invested in vDos, further development and support; keep vDos nag-free for most (99+%) users? 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 about new vDos versions. The current one does the job, if it isn't broken… I could be more open to your specific issues or wishes, and supply an intermediate pre-release to address those.
After filling out the registration form, you’ll receive a mail with an invoice and license file (if paid directly by Stripe). The license file is to be copied to the vDos.exe directory. That’s it, no further activation procedures or online validations. Transferring a registered vDos to other/new systems, remains a copy of some files (plus one).
vDos can be registered in two editions (they only differ in what vDos eventually checks for):
Registration is lifetime and remains valid for any new versions. If I would decide to change this policy, it won’t involve existing registrations.
User name: € 35 per user name.
The Windows user name has to be (one of) the user name(s) defined in the license file.

Networked: € 150.
The number of users is unlimited, as long the PC’s are joined to the registered domain or that network drive is addressed.

The required user name(s) or network ID for registration are shown in the nag, System Menu - About… in a framed vDos window, or issuing the
ABOUT command at the vDos/DOS command prompt.
You can (should) evaluate vDos for as long you feel needed to be confident it will fulfill your requirements. A vDos license can’t be revoked since there is no online validation. It will remain valid for the registered (future) edition it applies to.

That’s mainly also the reason why I don’t accept PayPal anymore. PayPal payments can simply be revoked. I trust credit card companies will actually review a complaint. Not just do a refund if the buyer doesn’t withdraw that.
Money back guarantee?
Is registration needed?
What will it bring?
How to register?
What about new versions?