bbPress.org

I am new to this plugin and to running a forum. I am just a volunteer English teacher obsessed with WP.
My user count will be microscopic, a handful of people. (my ESL students)
Many of my users will not have email addresses, have not ever used PCs and do not have PCs at home – experience has shown me it is impractical to provide email initially.

Is there an option to register users without email addresses?
If I leave the forums open without registration – what are the potential issues, security or otherwise? If any?

(I do not know how to set up any WP registrations anyway!)
– WP 4.1/bbPress 2.5.4. MultiSite install.
– I have dedicated a MultiSite subsite to bbPress.
– I have Askimet and Conditional CAPTCHA https://wordpress.org/plugins/wp-conditional-captcha/

Any suggestions or input about plugins, if this is a bad idea, etc. will be appreciated.