Changes include ( comments in Italics are my own; we are awaiting additional details/understanding  on most of these changes):

• Fixes an issue that prevents some Java-based applications from starting.

 Presumably a client fix for both desktop and RDS. The issue that is fixed with the client hotfix affects Java based application packages that have been experienceing the "max heap size" issue. For some customers this fix was critical.

• Fixes a Windows Explorer crash on a remote App-V 5.1 client when you are connected by using Remote Desktop Services. This issue occurs when you right-click File or Computer on the Start menu.

Presumably a client fix for RDS only.  This has been an outstanding issue on that client.

• After you publish a new version of an application in a Connection Group, the application version is now displayed correctly on the App-V Server User Interface (UI).

  Appears to affect the display of the App-V Management Server browser based management console.  This change appears to be cosmetic only and does not affect functinality.

• Fixes the App-V server UI to link to the updated Microsoft Privacy Policy.

Appears to be a consmetic fix to the brower based console of the App-V Management Server.

• Removes the dependency on Visual C++ 2005 for installation.

Not sure which installer this is affecting, but I'll guess it is affecting the server installer.  Except it is a hotfix, not a full install package.  I choose to just ignore this bizare item and hope it doesn't come back to bite us.

• Adds support for Slovakian and Slovenian versions of the Supplemental Notice. The notice is displayed during the client/RDS servicing release installation.

Well I trained 20 people in Slovakia that might care about this one..

The hotfix does not include a sequencer change.  Presumably, the Publishing and Management servers do not require updating.  I also presume that skipping the upgrade of the management server is an option for many customers.

App-V Hotfixes always include prior fixes on the same release.  In other words, you only need to apply the latest hotfix (5.1 HF3 in this case) and it includes other prior hotfices (5.1 HF1and HF2 in this case).

Client is version 5.1.104,  Server is 5.1.105.  I believe that you may apply these independently.  The Server hotfix appears to only apply to the Management Server and would not need to be applied to Publishing and Report servers (but check HF1, which is included).  The KB reports that you must reboot after applying the patch, so a maintenance window is needed.

Download from Microsoft Support Downloads: KB3144445 https://support.microsoft.com/en-us/kb/3144445