[lkurtz]

There are a couple of legitimate reasons, namely the expense/KYC process of an Apple Developer Program membership and/or the complexity of integrating signing + notarization into existing build pipelines (but XCode does makes it pretty straightforward to cut an ad-hoc release that is signed and notarized).

In my opinion at least, the most likely reason is that Apple is refusing to notarize the software. If this is the case, people really should not be running it.

[josephcsible]

Once you buy a Mac, Apple doesn't own it anymore, so them not wanting you to run a piece of software isn't a good reason why you shouldn't.

[dishsoap]

This used to be true. It is, in fact, not true anymore!

[margana]

Apple refusing to notarize it actually makes me want to use it more. That means Rossmann and his associates have got under Apple's skin enough that they would try to sabotage projects that he is involved with.