As all of the facilities used for access to the SMBIOS tables are base-OS features, the security and availability of the tables are based upon OS privlege levels.
For example, on Linux, access to the tables is through /dev/mem, and the OS security associated with this file is in effect. By default, on Linux access to /dev/mem is limited to the root superuser.
On Windows, access is through the "\\Device\PhysicalMemory" file. Access to this file is limited to the Administrator superuser.
It is also important to note that the Libsmbios code does not significantly enable anything that is not already otherwise possible to do on Dell systems. There already exist other utilities that read and parse SMBIOS tables on both Linux and Windows. Libsmbios simply provides a unified library of code that can be used by different project that will help control code duplication and wasted effort by diverse teams working with this data.
CMOS Tokens provide a way for BIOS to notify management applications about the mapping between specific features and bits in CMOS that can be controlled to enable or disable that feature. For example, one specific bit in CMOS may control the BIOS "Numlock at boot" feature. If this bit is on, the Numlock key is on during boot, if this bit is off, numlock is off. CMOS Tokens provide a "pointer" to find which bits to modify.
CMOS Tokens also control other features such as enable/disable PXE, boot order, enable NICs, etc. This method allows BIOS to move the physical location of these bits around in CMOS to best fit BIOS needs, while still allowing management applications to "find" where the bits are that need to be manipulated.
It is important to note that restricting this information does not protect the user, as a malicious attacker that has administrative access can completely wipe CMOS or manipulate CMOS without any special knowledge or access that Libsmbios may add.