Subscription to 1Password is not mandatory.
Or at least it was not in the past.
Without a subscription, you can create local vaults which can be synced via Dropbox, iCloud or over WiFi within the same subnet (which means over VPN too).
The subscription isn't really mandatory, but I've been quite disappointed at the transparency with which they've been pushing people towards that...even those of us that purchased the full version somewhat recently. For instance, the complete lack of a Windows version that isn't subscription based is a huge pain since I got a cheap Kodi box recently and my keyboard is a remote control that sucks for typing passwords.
I get that they want to transition people to that revenue model for their own benefit, but they haven't made a convincing argument that it's in our interests and they've definitely made those of us "offline" customers feel like second-class citizens. Normally, I'm all for subscription services, but password management is one area that I want complete control over and if they keep pushing me towards a model that requires their online presence, I'll end up switching.
And shameless plug for my own cross-platform powershell-based 1Password client, which can read both formats of local vaults: https://github.com/latkin/1poshword
I tried the v4, but it wouldn't accept my v6 license key :(
My workaround was to write a small utility that I run on both my Mac and Windows boxes that sits in the background and keeps the two clipboards synchronized. So I just copy from Mac 1p and paste in Windows. Not ideal, since it makes the browser extension useless, but it works well enough for the few times that I need to enter passwords on that box. But on the plus side, I can also use it for entering commands in cmd.exe and Powershell too.
I currently have 1password and 1password 6 installed. At some point I followed an "upgrade" suggestion, found out I don't get the upgrade for free and I had put new passwords into what is now an expired version.
I can't find how to purchase the single license for Windows. I found the download for Windows v4 and the single license purchase for Mac here: https://agilebits.com/store but not the Windows license.
Here is some documentation on the Dropbox sync for example: https://support.1password.com/sync-with-dropbox/