I have been setting myself up on a new computing cluster (CentOS 6.7), so I'm in the lovely land of installing things without root. tmux proved a bit frustrating, so here's what I ended up doing:
install libevent
tmux needs this, I didn't have it (you might, so try installing tmux first). Grabbed it from the repository, then:
$ git clone https://github.com/libevent/libevent
$ cd libevent
$ ./configure --prefix=$HOME
$ make
$ make verify # this failed for me, oh well
$ make install
Choose your prefix as you desire.
Now libevent should be installed in $HOME. Easy y0.
install tmux
Git all the things.
$ git clone https://github.com/tmux/tmux
$ cd tmux
$ zsh autogen.sh
Now for the thing which was required to make everything work, a slightly augmented version of the winning answer from this Stack Exchange post...
$ export LD_LIBRARY_PATH=$LD_LIBRARY_PATH:$HOME/lib # possibly optional, see below
$ DIR=$HOME
$ ./configure CFLAGS="-I$DIR/include" LDFLAGS="-L$DIR/lib" --prefix=$DIR
Obviously I could have used $HOME there instead of $DIR, but I am staying consistent.
$ make
$ make install
And everything should Just Work now. This probably shouldn't have posed the difficulty that it did, but I'm a scientist, not a sysadmin.
final thing
Does the LD_LIBRARY_PATH line seem redundant to you? It seems redundant to me, but I had to add it to my .zshenv (or, try .bashrc) after this to get tmux to continue working. May or may not have been necessary during installation (what with all that redundancy) but I'm not going to uninstall just to check, because tmux is actually working and if I look at it too closely it will definitely break.