wpler

<a href="https://www.wpler.com/linkmanager-fur-multisites/" rel="nofollow ugc">Deutsche Beschreibung des Plugins</a>
You run a Multisite Blogsystem with open registration for users to add own blogs and their can using a theme by 
different installed themes, but you want to show a link into the footers of the themes but only once time and for 
every blog another one?
With this plugin you can manage your outgoing links into the themes by a shortcode/function for every blog. You can 
set for every link the target, relation (Attribute rel), linktext and -title and the target url. Also you can set more 
than one link for a blog.
For output you can use a shortcode or a function . This function get the links 
for the current blog-id and printed this, if links are available.
All options/links can set by network admin only. The outputs needs no capability.

WPMU LinkManager

Manage your Themes footer links for every blog into a multisite includes with conditional tags.

Neerav D.

WPMS Global Content allow wordpress multisite network admin to set common header and footer content. These header and footer will be displayed in all child blogs. Its very usefull for displaying branding, advertisement and copyright message on all child blogs.
Admin can set content via familiar tiny mce editor or can paste html content.
Admin can provide comma separated list of blog ids to exclude from common header and footer.
For detailed documentation visit http://www.vareen.co.cc/documentation/wpms-global-content/

WPMS Global Content

Can add custom header script to all web on multisite wp

WPMS Global Content allow wordpress multisite network admin to set common header and footer content.

WPMU LinkManager vs WPMS Global Content