A PS:
man osalang and the osalang command itself reveal that JavaScript needs to have those two capital letters.
commands like:
osascript -l JavaScript '/Users/houthakker/Desktop/clipappend.applescript'
or
osascript -l JavaScript '/Users/robintrew/Desktop/clipappend.scpt'
Do run script files containing textual or compiled JXA javascript, despite provoking a retort like this:
2014-11-09 16:27:27.644 osascript[7530:562983] warning: failed to get scripting definition from /usr/bin/osascript; it may not be scriptable.