is "radiosilence" a safe app

Conspiracy theories are more fun, but your Mac is unlikely to have been invaded by something that is now making it hot.

To find out what might be going wrong, focus on the possible causes of the problem with some of these tools. Do not just club your computer on the head with a flint axe kind of solution.

If you believe you may have malware, run MalwareBytes.

If you want to check for known Bad Actors, mis-configuration, performance problems, or panics, use Etrecheck.

In each case, obtain ONLY from the developer (or Etrecheck is also available in a lightweight version from the Mac App Store).

No you should not run an antivirus app. And Windows users no longer run antivirus software. Newer versions of Windows have built in virus protection and just as with Apple computers, running third party anti virus apps interferes with the OS's own protections.

MalwareBytes is anti malware and is often recommended here in these communities.

The primary "claim to fame" for malwarebytes is its on-demand Malware scan.

Because people keep asking for it (because they have been marketed so hard by others) they have added features that allow it to stay on your Mac and do a little active checking, but nothing like most so-called Anti-Virus packages,

The main thing other anti-Virus scanners do is completely useless: They scan each and every file looking for patterns of bits that match known malware. They do not distinguish whether any of these patterns are in executable files or in raw data like picture files, where it could never be a threat because it cannot become executable. If found, they often deliberately crash your Mac "to protect you". Once completed, they begin again, which punishes performance doing work that never needs to be done anyway. Often, their libraries consist of really old Windows viruses that can not possibly run on a Mac. They market themselves by sowing fear among users.

What your Mac (especially El Capitan and later) already does is to lock all System Directories so they cannot be changed, checksum all Applications so that if they are somehow changed, they will not run, then make certain NOTHING can become executable except inside a limited "sandbox" that does not have access to system directories or system resources other than the ones they declared they needed up front.

The only things that can become executable automatically are signed by the Certificates of Registered Developers (which Apple can and does revoke if they screw up). To install anything not from the Mac App Store or a Registered Developer, it must be deliberately approved BY YOU, and you must never be complacent! The reason that box opens when you try to install Flash Player, is so that you can see it came from a site like get.adobe.com, not from Flash.HackerPardise.com, and approve or dis-approve its installation.

I can't speak as to the reason the hosts removed the link but links to third party apps that are of questionable value are typically removed so that less knowledgeable users don't inadvertently download an app that is of no value to them.