This is brilliant! I was looking for an engine for interactive fiction games since I've been writing for my whole life and meanwhile, I got involved in the video games industry as a QA in the last 6 years. Lately, I've been doing my best to delve into game design. Was looking for a jam that allows interactive fiction type of adventure games to be submitted and not only found one, but this way I found a really interesting tool! By the way, if ( god bless! ) I end up creating a game that I am really proud of, using Decker, is it okay to upload it to my own Itch.io page with a reference to you and the Decker page and even maybe put a small price on it?
You're absolutely free to distribute anything you make with Decker as you please, including selling your programs if you wish.
Submissions to Decktember should provide a free web-playable version, but there's nothing stopping you from making your submission a demo of a larger game or continuing to work on your project after the jam release.
Providing links to the Decker page is not required, but always appreciated. I rely entirely upon word-of-mouth to help other people find out about Decker.