I tried to install community edition of radzen components and I was asked either to accept trial period or enter a license key. I thought community edition is free to use ?
15 day trial period is for professional features only, Radzen will continue after 15 days with out professional features (i.e community edition).
The Radzen Blazor component are free and you can use them without installing Radzen. Check here for more info: Installation
Radzen itself will ask you to start a trial upon first installation. You register with your email and receive an activation code shortly after.