SwitchResX Licence terms
Basically, following terms apply, which are in fact common sense :
The software is provided as is from this web site. You download the software, you have 10 days to try it. If you're satisfied, you have oto register. Refunds after registration are not possible (see this FAQ item for explanation). After 10 days, if you don't register, the program will refuse to save any setting and you will have to remove it.
A single user license entitles you to install the program, without any time limit, on one computer and use it for all users of this computer; OR to install the software on two computers if you are the sole user of the computer and you don't use the both computers at the same time (example: one computer at work, one computer at home). You can use the same license on more than one partition or one hard drive of one identical computer (for example, in case of dual boot with two macOS versions, not both partitions are used at the same time). The main principle is that a single user license can only be active once at one specific point of time.
A site license entitles you to install the program, without any time limit, on all computers belonging to a legal entity (legal company, school, school district, non profit organisation...) and to use it for all users of these computers. There's no limit on the number of computers or users that can use the software if licensed with a site license.
Both licenses allow you to download current and all future updates of SwitchResX version 4.x, without any time limitation. There's no separate subscription or annual fee. The registration is once and for all. Updates are notified inside the software, and it's up to you to download and install the updates. However, any upgrade to a future major version (5.x or more) isn't guaranteed to be free. So far, I have no plans on such an upgrade. As an information, licenses and serial numbers received when registering SwitchResX 3 in 2002 are still valid today.
Once registered through FastSpring (acting as payment processor), you will receive two emails from FastSpring. The first mail is a payment receipt. The second mail contains your serial number and a link to your invoice. You are strongly advised to keep and archive these mails.
The serial number is needed to use the software without the time limitation. If you registered directly inside the software, the serial number would have been applied automatically. If you need to move the license or reinstall the software, you will have to enter the serial number manually. Keep your serial number safe.
I get a copy of the emails from FastSpring for information and for my accounting. I don't specially archive these emails and I don't keep any user data. As such I cannot guarantee I will be able to retrieve the data if you lose it. In particular, if you lose your serial number, I cannot guarantee that I can retrieve it for you.
Software support is not part of the software license. I do provide support for the software, registered or not, during trial period or after, by email only, on a timely manner. There's no guaranteed delay on the support answer, but I do my best. I provide software directly related to the software: use of functions, debugging, troubleshooting black screen after selecting a wrong resolution, but I cannot provide support for software I don't have control on (bugs in macOS, third party applications…) or for hardware (advises on adapters or cables, or on monitors). I will generally tell you if the scope of your support question goes beyond SwitchResX.