Not sure why there are so many concerns about a piece of software not working correctly with MacOS Mojave! It's a BETA product that has already passed through 14 iterations and isn't yet the final release version, so why would anyone expect (all) 3rd-Party software to work on it without any issues.
In my experience with MacOS for more than 10 years (and Microsoft for more than 30 years), every OS upgrade has necessitated a significant number of upgrades to software applications; and that includes Microsoft Office and all Apple application software, immediately after the OS update is released. 3rd-Party software developers need to understand what issues are likely to arise with each major new OS release, but very rarely release updates which attempt to keep pace with Beta changes simply because it's a constantly moving target until all changes are finalised. Lost count of the number of times Apple (and Microsoft) have trialled changes in Beta-OS versions only to change/adapt their original idea, or even drop/postpone significant changes entirely in a 'final' release version.
As others have mentioned its far better for the RootsMagic developers to expend there efforts on completing RootsMagic 8 than investing any serious amount of time investigating glitches experienced with running a non-native MacOS application through a 3rd-Party (which itself relies on another 3rd party piece of software - WINE) on a BETA OS.