One or two forum members at DPReview have recommended Reshade as a free alternative to upsampling software like Topaz Gigapixel AI. The Reshade website (http://reshade.com/) indeed says it is (as of 2017, apparently) free; however, it does not appear to follow any of the familiar models of open-source software, honor-system freeware, etc.
Can the forum members here tell me anything about Reshade and whether it is legitimate freeware without any dangerous / malicious components?
(As a semi-aside: this is my first post here. Another DPR forum member recommends this site. I’ve been using GIMP since 2003 or so, and CHDK since probably about 2010.)