What are Surnames' dataset usages?
The readme file lists the following uses for the dataset:

1. Cyber Security

2. Machine Learning

3. Recommender System

I believe that you already know point 3 since you specified that you want to use the dataset to build a recommender system.

About Point 2: You can use the information in the dataset to train a machine learning algorithm. The former could, for example, learn to recognize the relationships between surnames and nationality, therefore, after the training, you could pass one or more surnames as an input to the  algorithm and it could return the country.

About Point 3: 
Here the subject becomes wider: 
such a database can have great potential in the field of security. 
 For example it could be used to perform password penetration tests, towards servers, using the list as a dictionary. For this same reason, however, it could also be useful to any attackers with malicious intent. Another example: imagine you have gained access to a confidential database that stores all user passwords and usernames. However, these data are hashed. You could submit all dataset records to the same hash function and compare them with database hashes to see if you find matches.