Puzzle generators, duplicate content and licences

What KDP says about reused content

KDP's Guide to Kindle Content Quality lists, as typically disappointing, content that is freely available on the web (unless you own the copyright or it is public domain) and content that is excessively reused, recycled or repeated within or across books. For multi-volume works it says the same content may not be excessively reused across books.

A puzzle is content in this sense. If the same 100 Sudoku grids appear in your book and in fifty others, or in your volume 1 and volume 2, that is reused content.

Free websites, PLR packs and bought bundles

• Free puzzle websites. Many say "personal use" or "not for resale" in their terms. Some say "free for commercial use", which also means other publishers use the same puzzles.
• PLR (private label rights) packs and Etsy bundles. You buy a licence to a fixed set of puzzles that others have bought too. A KDP forum thread asks exactly this: whether licensed puzzles bought on Etsy can be published when other buyers publish the same ones.
• Old puzzle collections. Public domain does not mean unique; free copies may already be in the store.

What to check in a puzzle generator

1. Licence in writing. Does the licence allow selling the puzzles in printed books and PDFs, under your own name, without royalties? What happens to books you made if you cancel?
2. New puzzles per book. Does each book get new puzzles, or does every user draw from the same pool?
3. Reprints. Can you make the same book again for a reprint or a fix?
4. Proof. Does it check that every puzzle has exactly one solution, and that it can be solved by logic?
5. AI or not. If the tool uses AI to create content, you may have to disclose it to KDP. See AI disclosure.

Keeping your own volumes different

A series is where publishers most often repeat themselves by accident: the same generator settings, the same seed, the same puzzles in a new cover. Keep a note of which settings and seeds you used for each book, and make every volume from new ones.

How Gridbinder handles it

The Gridbinder studio calls no AI service: every puzzle comes from a generator and a solver written for its type (the fixed rule texts and word lists that ship with it were written during development, partly with AI writing tools; see AI disclosure). Each puzzle comes from a seed made of your subscription, the book code, the puzzle type, the level and its position, so different subscribers and different book codes get different puzzles, and the same code rebuilds the same book for a reprint. Very small easy grids, such as a 5 x 5 Slitherlink, have a limited number of layouts, so two of those can occasionally match. The subscription includes a commercial licence: sell the books on Amazon, Etsy, Gumroad or your own site, in print or as PDF, with no royalties and no credit to us, and books made while subscribed stay licensed after you cancel. You may not resell the puzzles as a pack for others to republish.