The best way to prevent accuse as a plagiarist is by writing your own, original content, and not copy-paste any other's. Most of the bounties have some rules that try to avoid people trying to earn some coins/tokens in exchange of copy-pasting the work of other members, and that's the way it should work so don't try to cheat the system.

If you want to earn some money, work for it. It's still not so difficult to do it, and you'll feel so much better with yourself building something on your own than plagiarising any other work that you'll agree with me it had been worth the effort.