Haram (; Arabic: حَرَام, ḥarām) is an Arabic term meaning ‘forbidden’. This may refer to: either something sacred to which access is forbidden to the people who are not in a state of purity or who are not initiated into the sacred knowledge; or, in direct contrast, to an evil and thus "sinful action that is forbidden to be done".
Muslim is not allowed to sell or take part in marketing or selling alcohol or pork. You should refrain putting such unlawful items on your website or platform. If you sell such Haraam items,bayou will be committing a sinful act, and every income from such work is Haraam as well.
You should keep your platform and business activities clean and pure from any Haraam business.
In regards to chess specifically, and playing it of course with no gambling, this is a fiqhi matter, where our esteemed Maraji' have different verdicts.
For example, A.U. Seyid Sistani (may Allah prolong his life) says that it is absolutely haram.
As for A.U. Seyid Khamenei (may Allah prolong his life), he says if it is commonly seen in the custom of people ('urf) as a gambling instrument, then it is haram, and if not, then it is halal.
You must refer to your Marja' taqleed for this fatwa.
And Allah knows best.