I saw tool from ubuntu web platform called documentation-builder https://docs.ubuntu.com/documentation-builder/en/ and this is what exactly I need for my product. And my product is commercial one. Can I use the HTML created by this tool for commercial purpose?
Based on a cursory look at the project, my answer would be that you can not use document-builder to build your documentation. Not for a commercial application nor for an open-source one.
This conclusion is based on the fact that I can't find any license information about the project and that the project copies a (non-trivial) template from its sources into the output.
The fact that non-trivial parts of the document-builder project are copied means that the output from the program will be considered to be a "derived work."
The fact that no license information is available means that the project defaults to the "all rights reserved" copyright status, which means that you are not allowed to create derived works.
These two facts combined make that documentation-builder is effectively unusable.