@ZG53
If you read all of the thread and the guidance notes...
The JAR files that ImageTrimmer uses must run/open in Java.
So firstly you need to have Java installed [if you don't already have it, the it's freely available off the www...].
Next you must ensure that the JAR files are set to open with Java, many unZIP/decompression tools like WinRar hijack that file type and open it themselves [uselessly]. Go into the associated filetypes in WinRar and untick .JAR...
ImageTrimmer should now run as intended, although to do need to ensure it's working on a PNG file Image with fully solid and transparent areas...

This license expired message occurs if you have an out dated copy of any one or all of the extension, LibFredo6 and the SketchUcation toolset [used for licensing].
It was originally issued with a time-limited trial period, but later Fredo decided to keep it free for the time being...
If you update of of these files and restart SketchUp, then that message should stop.
No license is currently needed...