Mixed experiences, think it depends on a combination of luck, account age, originality, and the skill(s) involved. I learned some basic scripting so that I could write my own scripts. Some I have used extensively and experienced zero bans with, others have had frequent bans. For example, a basic progressive WC script I made will get a fresh f2p account banned if used too much.
Don't think an original idea means no bans though. I have a couple of scripts doing stuff that no one else seems to do and I've still had one or two accounts banned doing it.
If you really want private scripts I'd suggest learning how to make them yourself. There are good resources and helpful people on here, and you can build them up in scope quite quickly. It's also good fun