Cathy,
there is no need to downgrade tcl to old versions. I am using aolserver40r10 with thread-enable tcl-8.4.15.
Just do:
CPPFLAGS="-nostartfiles" ./configure --prefix=/usr/local/aolserver40r10 --with-tcl=/usr/local/lib
to avoid error message
pthread.o(.text+0x0): In function `_init':: multiple definition of `_init'
You'd consider check your OS to prevent other related pthreads error. Before compiling check for GNU_LIBPTHREAD_VERSION at command prompt
# getconf GNU_LIBPTHREAD_VERSION
If return is "NPTL"+version you also need comment out line
pthread_kill_other_threads_np()
in nsd/unix.c
