[citation needed]

https://en.wikipedia.org/w/index.php?title=The_Unarchiver&oldid=920202335#cite_note-eula-2

Interesting.

As I do not see the source from which the package is compiled. And since that source carries an 
GPL 2.1 License.txt 

So either that EULA applies to only that binaries available at the referrenced site. 
(My reading of the situation) or it was a careless use of a boiler plate EULA not realizing the 
conflict. 

I'm not a licensing wonk so I don't fully understand how all that would fit together. But the 
source is not pulled from the site with the ELUA and thus may be Exempt.

For reference the surrent source is pulled from:

  https://bitbucket.org/kosovan/theunarchiver/get/unar1.10.1.tar.gz

"This software used to be free software, but isn't free anymore" is such an oxymoronic concept. This seems like a non-issue to me.

Any current or future releases of the proprietary freeware aren't being released as non-free source code as far as I can tell, so at worst this would be a rationale to fork the last GPLed code and carry on the torch yourself. Do you know anyone who is interested?

im not sure that unarchiver is needed - it was added to replace
unar, which was itself a replacement for unrar - i have heard
that bsd-tar can also open rar archives - if the only reason to
fork the project is so that parabola users can open rar archives;
then it may not be necessary

i.e. does this program do anything that other programs can not?

What precisely did you add? It's in [community] and synced from archlinux.

You should ask whether you have any reason to explicitly blacklist it. Other than the website pointing to some commercial continuation.

before arch added 'unarchiver', there was an 'unar' package in
[libre] that was exactly the same program with a confusingly
different name - after arch added 'unarchiver', the confusing
'unar' was removed

https://labs.parabola.nu/issues/1769

As I understand it only the package name is misleading so it probably needs to be fixed.

Wikipedia says that:

The Unarchiver is a proprietary freeware² data decompression utility [...].

But it also says that:

The corresponding command line utilities unar and lsar is free (libre) software licensed under the LGPL⁶ run on Microsoft Windows, Linux, and macOS.[7]

So both aren't incompatible. We just need to make sure that the command line utilities are indeed free software and check from time to time if it's still the case, and if not probably keep an old package or look for forks or remove it.