Once you purchase a starter, you can modify the code in any way you like. Your modifications should comply with our licensing terms. A Basic license allows you to create a single end-product (1 Android + 1 iOS + 1 PWA) from a starter/theme/template, while Extended license allows you to create multiple end-products from a starter/theme/template.
Please note - At any point, you should not create another template or starter from our products, and sell it on any platform so to compete with our business.
Check the licensing terms and conditions at Licensing page