Earlier quoted context omitted.
Everything about the etrecheck website screams "system optimizer scam!" and this comment does nothing but reinforce that feeling.
it's a very simple tool, to be sure. but come on, it's not like it's steve gibson wares ... the free version is perfectly adequate. it's simply an information gathering and reporting tool. anyone could write this tool themselves -- the mechanics of it are beyond simple. but like all sysadmin tasks, gathering the requirements is the hard part.
Alas, EtreCheck is far from simple. Early versions were little more than a wrapper around system_profiler. But the current version is very sophisticated (~40K lines of ObjC, C, XSL, XML, HTML, and JS) and has some one-of-a-kind features. (see above)