I can open it just fine with regular Notepad, Notepad++, and even Microsoft Word. Sounds like it's your computer problem rather than the dev doing anything on his end.Part of me loves the expanse of this game but another part of me hates how easy it is to miss content. I also have to wonder what you have done to the HTML file to make un-openable in Textpad. Never in my life have I seen any HTML file lock up a computer just by trying to view its code.
From a DRM perspective its effective at stopping cheaters and tweakers but at the same time it is still DRM at the end of the day.