ePud Bud
This tool can be found at: http://www.epubbud.com/
Similar to Papyrus, this tool is used to create eBooks that can be read by anyone online. However, this tool is much more hands on and requires a much more thorough understanding of the product in order to achieve results that look as nicely as Papyrus. Essentially, there is more to work with using this program, but to fully utilize all of this potential, one must be extremely competent with the tool. This site also has a built in component that allows you to buy eBooks and even sell ones that you have created.
ePub Bud is a tool that has similar uses in school as Papyrus, but is outclassed by Papyrus on nearly every level where they are similar. One distinct advantage is that it is possible to find and buy specific eBooks on ePub Bud, a feature that is not present in Papyrus.
In my opinion, this tool is not effective in creating a UDL environment for students. There is likely no group of students that would prefer to use this site over Papyrus, although it could be used to find additional resources for students to use through the eBook search features.
There is no minimum age to have an account, but it is explicitly required to have parental or teacher consent in order to apply if you are a student.
