You can take a look here to see that this is legit and not spam or malware:
http://forum.xda-developers.com/showthread.php?t=2079807
This app will allow you to easily manage what apps can be run in multi-window mode. Now you can run any app in multi-window mode.
REQUIRES ROOT & JELLY BEAN 4.1.2
Update 1.1.3- Added support for others.xml and dexed the code so it should run a little faster now
Update 1.1.2- Fixed a bug preventing apps from being selected by clicking directly on the checkbox.
Update 1.1.1- You can now filter applications by enabled and disabled state
Update 1.1- Added icons to the list and streamlined the code under the hood a little bit.
Update 1.01- Apps not checked in the manager will be added to the feature.xml file with a preceding "-". This is to fix a bug where some apps were retaining multi-window features even after un-checking them in the manager