If for no other reason, because it will let you have free access to many resources you may not own during the month of July. This is a handy way to test-drive some resources you may be interested in but are not sure about. For instance, want to know what you could do with the High Definition NT or OT? You can find out. Want to know whether that ICC volume would be a good purchase? You can find out.
The best part of the deal is this: FL has set this up in a totally fool-proof situation. When you sign up, you are NOT actually subscribed to the service. At the end of the month, there is nothing to cancel. Access will simply cease. If you did want to sign up longer term, you'd have to do that as a separate step.
Here is the link with more info:
https://community.logos.com/forums/t/105182.aspx
I don't know if there is a list of the resources one has access too yet.
EDITED the title to reflect some of the concerns some posters have (see below).