if you can't run couchdb on port 80.

It's because the user to run couchdb is (couchdb) who is not allow to run on port 80. You need to rebuild couchdb and change COUCHDB_USER to root as follows;

1. cd to your couchdb source code directory

$ cd svn/couchdb

2. change COUCHBD_USER to root

$ vi etc/default/couchdb

change COUCHDB_USER=couchdb to COUCHDB_USER=root

3. make and install it again.

$ make && sudo make install

4. then you can change couchdb local.ini configuration file to use port = 80. and restart the couchdb service again.