Yep, the TRUSTEDPATHS mechanism is a recent security feature which helps prevent unintentional loading of "planted" hostile executables. TRUSTEDPATHS is basically a "white list" which tells AutoCAD the locations from which it's safe to load plugins and scripts.
http://knowledge.autodesk.com/support/autocad/learn-explore/caas/CloudHelp/cloudhelp/2015/ENU/AutoCA...
The recommended practice is to install your app to a folder which is in AutoCAD's TRUSTEDPATHS list, or to instruct the user (or CAD Manager) to add your app's folder to the TRUSTEDPATHS list.
Going forward, the recommended practice will be to digitally sign your application's executable files, so that AutoCAD will recognize that it's from a trusted publisher regardless of the location from which it's loaded.
http://knowledge.autodesk.com/search-result/caas/CloudHelp/cloudhelp/2016/ENU/AutoCAD-Customization/...
In AutoCAD 2016, you can sign lisp files, but unfortunately you can't yet sign VBA dlls.