Just to understand, there is no free version for Katalon Runtime, correct? Like we have Katalon Studio (Free) vs Katalon Studio Enterprise (Paid)?
Correct. Katalon Runtime Engine is a separate product with a separate, paid license.
Can we buy just standalone licenses for KRE, and use those along with Free Katalon Studio version? Or do need to have Katalon enterprise edition for using KRE?
You can use KRE with KS free version, they are separate products with different licenses.