This happens when you try to download the html page and rename it to .cs. To download a plugin from a GitHub repo, either download the whole repo as a zip via the code the green Code button, then extract the .cs file from it, or click on the .cs file, click Raw, then right-click and select save as.
NVM, this is making me look like a liar, it's stopping now.
Got it downloaded... One thing I noticed, if you add wood to your furnace and turn it off... it keeps burning the wood in the furnace although the animations show the furnace should be off. It seems to only be happening with the large furnace, the regular furnace turns off as it should.
Thanks.