Jeroen Noomen released two new Polyglot opening books: Daring.bin and Variety.bin. A developer asked on the TalkChess forum whether they could bundle these books into a commercial iOS chess app for the Apple App Store, with proper attribution to Noomen in the legal notices.
Rebel, a moderator, gave a straightforward answer: ask Jeroen Noomen directly. No permission, no redistribution. The books carry licensing restrictions, and commercial use requires explicit approval from the author.
This is a common friction point in chess software. Opening books represent thousands of hours of analysis and curation. Even when creators distribute them freely or cheaply, they retain control over how developers use them. iOS developers can't assume free use means free commercial use. Noomen's books are popular precisely because they're well-researched and well-maintained. That value comes with strings attached.
The lesson here applies beyond Noomen's books. Any serious developer working with third-party chess resources needs to secure licenses upfront. A quick email beats app rejection or a cease-and-desist letter later.
THE TAKEAWAY: Commercial apps can't redistribute opening books without the author's permission, even with attribution.