There are some more info about ScummVM on the official site
http://www.scummvm.org/ And that's allso the best site to download it from I would say. I've been using it for quite a time now without any problems with adware or anything like that, so It's pretty safe.
And BS4 Will most likley not run on your system, I had a hard time getting it to run good on my brand new laptop and had to run it on minimun graphics to avoid the mouselag problem.