I recently created a group in SAP JAM available as a service on HCP trial. My login id is same as that of SCN (thanks to SSO) which is a P* userid. After I created the group I realized that I was not able to invite people to join the group. With little search I found that "External group" option has to be activated to enable people to be invited. I found a document on SAP Jam to be able to do the same. Here is a quick snapshot of the same:

From the settings on right hand side of the JAM one has to choose admin:

In the next screen expand Product Set up option and select "Features".

In the Features page scroll down and enable "External group Creation" option.

This would enable external invitation option in the group.

Thanks!