Linux is an open-source operating system, and many of its distributions (e.g., Ubuntu, CentOS, Debian) are available free of charge for both desktop (workstation) and server use. This model allows a company to deploy a single, consistent OS across its infrastructure without incurring licensing fees, which directly addresses the requirements stated in the question. The open-source nature also provides flexibility and extensive community support.

B. Windows: Both Windows desktop (e.g., Windows 11 Pro) and Windows Server editions require the purchase of licenses, often on a per-user or per-core basis.

C. macOS: This operating system is proprietary to Apple and is licensed for use only on Apple hardware, making it unsuitable for general server deployment and not free.

D. Chrome OS: This is a lightweight, cloud-focused OS primarily for specific hardware (Chromebooks) and is not designed or typically used as a general-purpose server OS.

1. The Linux Foundation. (n.d.). What is Linux?. "Linux is also distributed under an open source license... you can run Linux, without any licensing fees." The document also highlights its use on desktops and servers.

2. Canonical Ltd. (2024). Ubuntu Desktop and Ubuntu Server. The official Ubuntu website details that the operating system is "free to download, use and share" for both desktop and server environments.

3. Massachusetts Institute of Technology (MIT) OpenCourseWare. (2016). 6.033 Computer System Engineering, Spring 2009. Lecture 20, "The UNIX legacy; The open-source movement." This course material discusses the history and licensing models of operating systems, contrasting the proprietary model of Windows with the open-source model of Linux.