What is this aversion to Rust on online forums about?

It's not like there is aversion overall; you're seeing two effects:

1. people being really excited by Rust, learning Rust, using it for hobby projects, rewriting things in Rust etc.

1.1. sometimes the excitement has downsides - people get carried way, they get too preachy, they exaggerate how good it is, they insist on using Rust in places where it doesn't belong, they refuse to listen to criticism, they bring it up any time programming languages are discussed, they start acting a bit cult-ish

2. as a result of 1.1, when a positive Rust post comes up some people will have a negative reaction. Sometimes it's negative in a reasonable way that counteracts the exaggerated excitement and sometimes it's a more general feeling of "oh not this again".

So some people have aversion to Rust some of the time, there's still plenty of other people who like Rust or don't care too much about it either way.

Perhaps the actual question would be why Rust is being talked about so much in online forums. The answer is possibly active marketing that went viral and thus organic, although I assume the active part has gone down after Mozilla let many of those people go.

Reading the thread it seems people complain that the source code is not available, and that posting this (very nice) app using the "Rust" keyword might therefore be perceived as clickbait, as people would of course like to see how it's done in Rust. I tend to agree as I would like to learn more about the app (since I've done Rust development for mobile and am curious how e.g. you generate bindings etc.), but unfortunately that seems nowhere to be found.

Rust language has pros and cons, like everything. Rust community sometimes exhibits this "everything needs to be rewritten in our favorite toy language, NOW" attitude that reminds me of worst times of Java hype.

Then again, every attempt at dethroning C++ came with it's own crowd of fanatic cultists, so maybe it's just that C++ is cursed.

I hate Rust. It's too time inefficient and hard to learn and the error messages don't make sense. There is already too mich choice in tools to use and its community is very Hipster.

Honestly no idea. I would ignore them. App looks nice.