How do the trial periods work?

The first installation starts a 14 day trial period: There are no restrictions on what you can do with Actions for Obsidian, no login, and no request for credentials.

Once the trial period is over, you can continue to use the application without any restrictions, but you will be reminded to purchase a license when one of its Shortcuts actions is triggered. The likelihood of this reminder dialog box appearing increases by 5% each day and is recalculated each time you use one of the AfO Shortcuts actions. This prevents a hard "trial period over" cut-off and gives you a few more days to test.

Once you buy the app, those reminder will go away.