Is OpenShot Video Editor safe to use? By the looks of it, it hasn’t been notarized by Apple. I don’t even know if it’s compatible with macOS Catalina or macOS Big Sur.
Information online has been a bit confusing.
Impossible to say with certainty, of course. It’s entirely possible that it’s safe. It’s possible it’s not.
Odds are good that it’s safe, since malware is rare on the Mac.
If you decide you want to run it, double-click on it. The first time you’ll get a warning about not being able to check it for malware.
Click “OK” and then Option+Click the icon and choose ‘Open’.
This time you’ll get a similar warning, but there will be an option to open it anyway.
Well, they have a Wikipedia page.
Do they have to manually ask Apple to notarize the app? Is it done automatically?
Malware infections are still possible though, right?
How can I encourage them to notarize their app? 
Even legitimate apps can be compromised. Notarization allows Apple to protect customers by blocking compromised apps from launching.
The process that I described above bypasses that security.
Notarization is somewhat like a seatbelt in a car. It can’t stop you from getting in an accident, but it can provide some protection if it happens.
Notarization is a fairly automated process; however, it will require a paid developer account ($99/year) which may be why they don’t want to do it. Some of these open-source folks have some strong negative opinions about Apple and their understanding of “freedom”.
Probably by whatever means they take feedback. I’d be surprised if they were unaware of the negative implications of their decision, but it can’t hurt to ask.
I have seen other open-source projects like Blender that are willing to pay the annual $99 fee. It would be quite strange for OpenShot Video Editor to be supported on macOS, but not pay the annual $99 fee for notarization. This is the first macOS app I have seen that hasn’t been notarized.
It looks like they have Facebook, Twitter, Reddit, and YouTube.
If anybody would be willing to help me raise their attention, that’d be great. 
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Twitter
Reddit
YouTube