Your License Key is an alpha-numeric string that uniquely identifies your video requests to the media servers. Unlike a User ID, or Account ID, the License Key recognizes anyone that views the videos that you have purchased AND assigned IP addresses to.
The typical use of the License Key is to clarify who should "get credit" for the video being viewed - this IS important for statistical and reporting purposes. A typical example of this is if you, the Account Owner, licensed the Shakespeare plays for your institution and assigned your schools IP addresses. Later, the same Shakespeare plays are licensed through a 3rd party such as a consortium, and your school is included in that licenses as well. At this point, a user can certainly watch the video because the IP address is on two Licenses. The problem arises when statistics are reported - that user watch a video, but which License report should show the view? If you do not specify that it's your license being used, that statistic may very well show up on the report for another license.
To avoid this problem, you should specify your license in the video link that you distribute, similar to this:
http://videos.ambrosevideo.com/?SH-001 should be http://videos.ambrosevideo.com/?SH-001&license=9FSW-LRMR-XQ68
This will insure that anyone that all viewers that watch a video from your licensed collection, will be recorded accordingly.