Continuing to have the same problem with squirrel-sql-snapshot-20171018_2131-MACOSX-install. Exact same symptoms (won't open, calling from Terminal gives same error). Upon investigation, Jorn's recommended changes (the missing -x) https://sourceforge.net/p/squirrel-sql/bugs/1310/#0aee were not in the squirrel-sql.sh. Once I pasted in the script from that post, I'm able to double-click SQuirreLSQL.app and it runs fine. (I had installed that snapshot over a 3.8 install...perhaps the new install didn't...
Continuing to have the same problem with squirrel-sql-snapshot-20171018_2131-MACOSX-install. Exact same symptoms (won't open, calling from Terminal gives same error). Investigating...any suggestions? java version "1.8.0_131" Mac OS 10.12.6 Sierra