Daniel Westermann-Clark

By default, WordPress network usernames cannot contain anything but lowercase letters and numbers. This plugin adds network options to let you include hyphens, underscores, or uppercase letters, if desired.
Furthermore, this plugin gives you the option to allow email addresses as usernames, or to allow all-numeric usernames (e.g. “1234”).
Finally, this plugin lets you override the minimum length for usernames (which defaults to four characters).
To follow updates to this plugin, visit:
https://danieltwc.com/
For help with this version, visit:
https://danieltwc.com/2011/network-username-restrictions-override-1-0/

Network Username Restrictions Override

Does what it says!

Override restrictions on WordPress network usernames.

3dperuna

WPMU has great themes and plugins. Unfortunately, many, if not most, come with a nag notice that admins see about installing their notifications dashboard plugin. If you’ve bought one plugin for your site this is probably overkill. If you’re a developer you don’t need this on your client’s sites.
This is a simple plugin that removes the notice. The 1.3 version has been checked against WP 4.4 and recent WPMU plugins, but still should be backwards compatible with older versions of WPMU plugins.
Note: If you do decide to you install the WPMU notifications plugin, please deactivate this one first. Errors may occur if you don’t.
If you like this plugin consider donating: http://www.protospace.com/wpmu-no-nag-plugin/

Remove WPMU Dashboard Install Nag

Works as advertised. Now, why a plugin should be needed for this is another question altogether, and installing and activating this plugin is no substitute for filing an RFE to either add a close button to those annoying nags or a switch to turn them off (and their pref doesn't always work, apparently).
Thanks for this!



Simple and to the point

This plugin removes the nag notice at the top of WPMU plugins and themes.

Network Username Restrictions Override vs Remove WPMU Dashboard Install Nag