Please don’t use
the “~/local/share/check_mk/checks/” is way better for own checks. The first folder is not update safe.
I had a look at the check from the article and this will not work with actual 2.0/2.1 CMK versions. It is very old style.
You can test if this check has any syntax problems with “cmk --debug -vvII hostname”.
If this runs without any problem than also this very old check should work.