madebygift on "Shoreditch theme throws jetpack.php error on Multisite"

Are you both running a version of PHP older than 5.5, by any chance? We were able to replicate this error on a server running PHP 5.4.4.

You could try changing line 129 of /inc/jetpack.php from this:

if ( is_home() && ! is_paged() && ! empty( shoreditch_get_featured_posts() ) ) {

to this:

if ( is_home() && ! is_paged() && false !== shoreditch_get_featured_posts() ) {

This should hopefully take care of the error -- which comes from a change in the behaviour of the empty function (reference) and allow you to preview or activate Shoreditch normally.

We will also regenerate a new version of the theme that you'll soon be able to update from your Themes dashboard or download on WordPress.com.

Thanks for bringing the error to our attention and apologies for the inconvenience.

Forgive me if this is the wrong forum, but I couldn't find a specific forum for the new WordPress theme (on wordpress.com only at the moment).

No worries, this was the right place! We've submitted Shoreditch to the WordPress.org directory, but it's still in the review queue. Once it's accepted it'll have its own support forum. In the meantime, if you need further help with the self-hosted version of Shoreditch, you can post in the WordPress.org general themes forum:

https://wordpress.org/support/forum/themes-and-templates

Tag your post with wpcom-theme in the tags area -- as someone did on this thread -- to be sure it will get attention:

https://cloudup.com/c4b6HOXuhVG