There are many iLO features that are free. You can view this data sheet to see a comparison of the features of the various license types and iLO standard
http://h20195.www2.hp.com/V2/GetDocument.aspx?docname=4AA4-5167ENW&cc=us&lc=en
What do you want to do with iLO, that pretty much dictates if you need a license or not.