The phrase "are free to modify" is correct and usable in written English.
You can use it when giving permission or indicating that someone has the liberty to make changes to something.
Example: "You are free to modify the document as you see fit to better suit your needs."
Alternatives: "are allowed to change" or "have the liberty to alter".
You are free to modify the database to add more characters for use with Chinese Reviewer.
In the open source model of development, the code is distributed free and programmers are free to modify and debug it, within certain rules.
Open-source software, which developers are free to modify and redistribute, is seen as the antithesis of proprietary software like Windows.
Departments are free to modify these suggested job duties to fit departmental needs while ensuring compliance with campus ergonomic guidelines, labor contracts, and applicable regulations.
For Poincaré, since theoretical principles are conventions, we are free to modify them, but experiential reports are perfectly stable.
As always, device makers are free to modify Android to customize any range of features for Android devices.
The landlord was free to modify the deal's terms and charge whatever the market would bear, Mr. Kassenoff said.
He might require Microsoft to license Windows to several other companies that would be free to modify it and compete against Microsoft.
The trustees/servicers would be free to modify mortgages in order to maximize recoveries, and at the same time reduce foreclosures.
When corporations become destructive of those ends, or when we see ways to improve them in any way, we should be free to modify them as we see fit.
This device is "opensource", so that readers will be free to modify the program, which includes adapting it according to their own needs or adding new features.
