Thank you very much for your answer! Using your advice, I successfully installed the VLC media player 2.2.2 Weatherwax on Linux Mint 18.3 running form a Live USB. Then, I just downloaded both Powder Player and Powder Web, extracted the folders from the downloaded archives for Linux in the "Downloads" folder and it worked to start Powder and PowderWeb by just clicking on these files!
Now I am enjoying the documentaries from VideoNeat.com streaming from magnet links on my PC and on my local network to a TV equipped with Chromecast 3 :)
I have OS X El Capitan Version 10.11.6, re-downloaded just to make sure it works and it works fine.
Please make sure you also take note of the steps from this page: http://powder.media/installing
This needs to be done because I didn't buy a software certificate for Powder Player yet.
About the update directory, there is no auto-updater for Powder Player v1.10 yet, you should just overwrite the Powder Player app you currently have installed after opening the dmg file.