Absolutely free demo version is available on the downloads page. But demo version has save and export feature limitations. 


Trial license key for Professional edition of PhotoScan can be requested via online web-form:

http://www.agisoft.com/downloads/request-trial/

The same key is valid for Agisoft Metashape Professional.


Note that both Standard and Professional editions of Metashape 1.5 allows to run the fully functional trial from the Activate Product dialog without a need of requesting trial key.