I think you mean services, not servers.
According to O'Reilly's "Running Linux": "The Linux kernel is a monolithic kernel, in that all core functions and device drivers are part of the kernel proper. Some OS's employ a microkernel architecture whereby device drivers and other components (such as filesystems and memory mgmt code) are not part of the kernel - rather they are treated as independent services or regular user applications. There are advantages and disadvantages to both designs......"
That being said, I concur 100% with ilikejam's comments, in that Linux does give you the choice to have certain modules either built-in or load-on-demand. -- J.W.