Scripts like this are usually created by independent developers (like those on aescripts + bcom). Buying the tool supports the creator so they can keep it compatible with new versions of After Effects. How to Get it Legally (and Cheaper)
If you are on a tight budget, you don't necessarily have to resort to risky downloads: true comp duplicator v3 free download
There are free scripts like rd_DuplicateComp (part of the rd_scripts bundle) that perform similar basic functions without the cost. Manual Workaround (The Free Way) Scripts like this are usually created by independent