As far as I know Lithium doesn't have any dependencies on glibc at all. Are you talking about running the mod on a server or are you talking about R1q2 as a client?
If you need to run the Lithium mod server, I recommend downloading the v1.31 source from http://www.quake2lithium.com
and building it on your CentOS system. Unpack the source zip file, open a terminal to the source folder and invoke 'make'. The source builds without errors on all my local versions of Linux, including OS X.