You cannot run the Splunk App for Windows Infrastructure on Splunk Free. It must run on Splunk Enterprise.
Is that something new in Version 1.1.1??? Previous versions worked and I bet that this one would as well if there was a way to assign the new role created by the install to the admin user.
BTW... I am running Splunk on a LINUX machine using the Splunk_TA_Windows version 4.7.3 on the Windows machine I am monitoring. It is a standalone machine running stuff that I need to keep an eye on and is not a member AD.