From the core book:
Anyone may publish free or commercial material based upon and/or declaring compatibility with “Troika!” without express written permission from the publisher, the Melsonian Arts Council, as long as they adhere to the following terms:
If your product declares compatibility with Troika! you must state the following in your legal text and on any websites from which a commercial product is sold: “[product name] is an independent production by [publisher name] and is not affiliated with the Melsonian Arts Council.”