Software simply being FOSS does not equal trust. It never has, and never should.

A free program certainly doesn't make it trustworthy.

edit: as pointed out, free stands for liberty to do as you please, not the financial definition. With that in mind, I definitely wouldn't call Grayjoy FOSS due to the license. I like my made up classification, but maybe this would work better; ROSS, "restricted open source software."

An open source program doesn't make it trustworthy. Unless you vet the program yourself you can never be 100% trusting.

For most of us, we're trusting the smaller community of people who actually go through the code for us. We don't trust individual pieces of FOSS, we trust the FOSS community and recognize that a developer is less likely to place malicious software in the code. However, it's also much easier for a malicious 3rd party to fork the program and infect the code.

I'm confident that anything FUTO puts out is going to be heavily looked over by all the Louis haters and fanboys - if they're up to something shady, we'll hear about it.

This particular software is what I'd call Open Source Donation Ware (OSDW)

"please pay us but we aren't checking if you do. Here's the code, if you want you could copy it and remove the payment all together. However, we retain the legal right to destroy any fork that adds spy/malware."

As a model, I can respect it. It's a good medium between releasing the program to the wild and being closed source. It's also a good model for making money for their work, pretty much like winrar's approach (rip now that windows is finally getting native .rar support). Yes, some programs are more subtle with a little coffee cup button, but as long as it doesn't constantly nag you, I'm okay with a more prominent 'donation' button.

What exactly do you mean by "trust", here? Yes, it's not fully FOSS, and I do understand why you wouldn't like or use it because of that, but you can still verify the code, compile it yourself and build and run it with your own modifications, so how would being fully FOSS make you trust it more?

Not sure what part of a free YT+ frontend that doesn't require permissions or an account you don't trust, but the reason is they don't want people to fork it freely and spread a version with malware, like happened to NewPipe.