CUNY Academic Commons

r-a-y

User registration spam is prevalent in BuddyPress.
One way to dramatically decrease signup spam is to restrict the email address domains that users can sign up with.
WordPress multisite has a native option called “Limited Email Registrations”. But this option requires you to enter the full email domain. For example, if you only wanted to allow .edu email addresses to register, this is not possible.
This plugin restricts registrations to the email domains that you specify and works in WordPress single-site and multi-site.
Plugin was developed for the <a href="http://commons.gc.cuny.edu" rel="nofollow ugc">CUNY Academic Commons</a>. Licensed under the GPLv2 or later.
<a href="https://github.com/cuny-academic-commons/bp-rsed" rel="nofollow ugc">Follow development on GitHub</a>.
Tested on BuddyPress 2.5, but should work all the way down to BuddyPress 1.6.

BP Restrict Signup by Email Domain

Only allow users with email addresses from certain domains to register in BuddyPress.

BuddyDev

Brajesh Singh

WordPress Username availability checker for WordPress & BuddyPress checks for the username availability on new user registration screens. 
It assist users & site admins by notifying them using ajax whether the username they entered is available or not.
<h4>Features</h4>
<ul>
<li>Checks for username availability in WordPress Admin New User screen</li>
<li>Checks for username availability on WordPress standard registration page</li>
<li>Checks for availability on BuddyPress registration page.</li>
</ul>
For screenshots & more details, please visit <a href="http://buddydev.com/plugins/bpdev-username-availability-checker/" title="Plugin page" rel="nofollow ugc">BuddyDev Username Availability Checker plugin page</a>
Free & paid supports are available via <a href="http://buddydev.com/support/forums/" title="BuddyDev support forums" rel="nofollow ugc">BuddyDev Support Forum</a>. Please Use BuddyDev support forums for your support requests. We may not be able to keep an eye over WordPress plugin support forum.

WordPress Username Availability Checker

WordPress Username availability checker checks if a username is available or not.

BP Restrict Signup by Email Domain vs WordPress Username Availability Checker