It then pointed me to https://support.apple.com/kb/DL1572?locale=en_USYou must install an older version of Java SE 6 Runtime to open “xtimecomposer.app”
The Java About box showed me this on High Sierra:
I think this means that JRE is 1.8.0_144 (maybe it came from El Capitan and that Apple had washed their hands completely on these Java matters).A critical Java security update is available.
8 Update 151 12 (74 MB)
Your current version is Java 8 Update 144. It is recommended that you update now to get the latest security fixes.
I then downgraded by using the url above and xTIMEcomposer was happy; JRE didn't complain about xTIMEcomposer's usage I assume.
The About box showed the same text as above. I had gotten 1.8.0_144 even if I had had it and had got a complaint?
But then I upgraded Java as suggested. I now have Java 8 Update 151 ie. Java Runtime 1.8.0_151.
But xTIMEcomposer 14.3.2 now works, without complaint! (NO it doesn't, I had not discovered the problems below)
I am confused. Maybe the list above indicates that. I'd be less confused if anybody could explain!