Where we can find the icon of components used in webix form-builder
Please check this information in our documentation
You can set any icon, just need to know that Webix provides two predefined sets of icons depending on the used skin: Webix Awesome Icons(Font Awesome 5 collection) and Webix Material Icons(Material Design Icons collection)
Is possible to have the source of: webix form-builder
I must admit that Webix Form Builder is a licensed tool which is distributed separately from main Webix package. Therefore, if you would like to use the source code of Webix Form Builder, you need to purchase a license.
If you are interested in purchasing, so please, contact tatsiana@webix.com