The author of a script can disable it whenever he wants. Good reasons for that are:
He needs to fix a bug, it can not be enabled while he edits the source code.
He is adding new features to the script so that it can work with more challenges.
There is a known bug that is serious enough to turn the script off until he/she has the time to fix it. Which may be both days and weeks since the scripts are created by the community, and they often do other things in their lifes as well.
Normally the above (the two first at least) is done in a temporary script instead if it's edits that will take some time. We only recommend disabling live scripts if the disable time is expected to be quite short. Preferrably minutes, and not above an hour.
Added to the above, a tag creator can disable his tag as well. Reasons for that is similar with the above. The "error" message will be the same "script disabled", even if it's actually the tag that is disabled.