Trumbowyg is an MIT-licensed open source project and completely free to use.

However, the amount of effort needed to maintain and develop new features for the project is not sustainable without proper financial backing. You can support its ongoing development by being a backer or a sponsor on Trumbowyg Patreon campaign (recurring, with perks for different tiers), and get your company logo here.

Also, you can make a one time donation via PayPal.