Yes, it is allowed! 
Xcurt's free plan can be used for commercial purposes, such as promoting products, services, affiliate links or sales pages. However, it is important to remember that this plan displays ads on the shortened links and has some limitations compared to the paid plans — such as less customization, a limit on monitored clicks and no priority support. 

If you want more professional features, such as: 

100% ad-free links 

Complete and detailed statistics 

Custom and branded URLs 

Smart redirection by country or device 

We recommend considering one of the paid plans, which are ideal for intensive commercial use and more advanced marketing strategies.