Is there a discount for existing OF2 users still?
I recommend checking out Buying Omni applications for Mac and contacting the Omni Group if you have specific questions.
A heads up that this forum is intended to be a place for users of Omni’s products to share information, so it’s best to contact Omni directly for support-related inquiries. This post provides more information.
Is iCloud sync still only possible if you purchase via the App Store?
OmniFocus has never support syncing over iCloud. You can use the free Omni Sync Server that’s provided by the Omni Group or your own WebDAV server. Omni Sync Server makes sense for most people.
Is it compatible with 10.13 High Sierra (I know, I know…)?
OmniFocus 3.11 requires macOS 10.14 or later. The downloads page includes a link to OmniFocus 3.4.6, which is supported under macOS 10.13. Though, I’d recommend upgrading to at least macOS 10.14 and using the latest release, if possible.
I hope this helps.
