First of all, I can't grab the latest snap, cause it seems to be down:
21  s6-0.border1-7206.valinux.com (209.81.23.54)  220.562 ms  236.556 ms  188.829 ms
22  fe0-0.dist6-3662.valinux.com (198.186.202.90)  254.845 ms  215.478 ms  225.191 ms
23  * * *
24  e2-1.community8-bi8000.valinux.com (198.186.202.94)  4075.988 ms !H * *
25  * e2-1.community8-bi8000.valinux.com (198.186.202.94)  3849.621 ms !H  3933.993 ms !H

Secondly:
Apache version: 2.0.16
configure flags:
LDFLAGS='-L/weblib/local/lib' CPPFLAGS='-I/weblib/local/include -I/mysql/include/mysql' ./configure \
        --prefix=/php4 \
        --with-config-file-path=/php4/lib \
        --with-apxs2=/ap2/bin/apxs \
        --with-mysql=shared,/mysql \
        --with-mhash=/weblib/local \
        --with-sablot=/weblib/local \
        --with-expat-dir=/weblib/local \
        --with-zlib=/weblib/local \
        --with-mcal=/home/mdev/_src/libmcal \
        --enable-calendar \
        --enable-sockets \
        --enable-ftp

Error:
Making all in apache2filter
make[2]: Entering directory `/usr/home/mdev/_src/php-4.0.5/sapi/apache2filter'
make[3]: Entering directory `/usr/home/mdev/_src/php-4.0.5/sapi/apache2filter'
/bin/sh /usr/home/mdev/_src/php-4.0.5/libtool --silent --mode=compile gcc  -I. -I/usr/home/mdev/_src/php-4.0.5/sapi/apache2filter -I/usr/home/mdev/_src/php-4.0.5/main -I/usr/home/mdev/_src/php-4.0.5 -I/ap2/include -I/usr/home/mdev/_src/php-4.0.5/Zend -I/home/mdev/_src/libmcal
 -I/weblib/local/include -I/mysql/include/mysql -I/usr/home/mdev/_src/php-4.0.5/ext/xml/expat/xmltok -I/usr/home/mdev/_src/php-4.0.5/ext/xml/expat/xmlparse -I/usr/home/mdev/_src/php-4.0.5/TSRM  -I/weblib/local/include -I/mysql/include/mysql -I/pgsql/include -DSUPPORT_UTF8 -DXML_BYTE_ORDER=12 -I../TSRM -g -O2  -c sapi_apache2.c
sapi_apache2.c: In function `php_input_filter':
sapi_apache2.c:248: too many arguments to function `ap_get_brigade'
sapi_apache2.c: In function `php_register_hook':
sapi_apache2.c:443: warning: passing arg 2 of `ap_register_input_filter' from incompatible pointer type
make[3]: *** [sapi_apache2.lo] Error 1
make[3]: Leaving directory `/usr/home/mdev/_src/php-4.0.5/sapi/apache2filter'
make[2]: *** [all-recursive] Error 1
make[2]: Leaving directory `/usr/home/mdev/_src/php-4.0.5/sapi/apache2filter'
make[1]: *** [all-recursive] Error 1
make[1]: Leaving directory `/usr/home/mdev/_src/php-4.0.5/sapi'
make: *** [all-recursive] Error 1

I 'quick-fixed' this as follows:
$ diff sapi_apache2.c sapi_apache2.c.org
247c247
< /* QUICKFIX -> This should be properly done by PHP developers
---
>
249,252d248
<               return rv;
<       }
< */
<       if((rv = ap_get_brigade(f->next, bb, mode)) != APR_SUCCESS) {

It then compiled only with a warning:
sapi_apache2.c: In function `php_register_hook':
sapi_apache2.c:447: warning: passing arg 2 of `ap_register_input_filter' from incompatible pointer type

And on installation with a libtool message:
libtool: install: warning: remember to run `libtool --finish /usr/home/mdev/_src/php-4.0.5/libs'

Activation is only partial - the "<FILES *.php>" directives we're not implemented in httpd.conf.

So far - phpinfo() looks good, though.