Hello.
That page is written in Japanese, so it probably be hard to understand the usage of it for non Japaneses.
Now I (the author of it

) will try to write the instruction. Sorry in advance for my poor English...
1. What is "WordPress Integrator"?
WordPress Integrator (WPI) is a set of a snippet (WordPressIntegrator) and a plugin (WordPressRouter).
Former captures the output of your WordPress. Latter will seize requested URL like
http://example.com/wpi_blog/2007/03/15/howtousewpi and call the document where WordPressIntegrator-snippet is placed.
2. Requirements
- MODx 0.9.5
- WordPress 2.0.5, ME 2.1.2 (some modification required)
mod_rewrite and friendly URL (but NOT alias path) is also required.
3. How to use
3-1. download the wordpressintegrator.1.0.1.zip from
http://nanabit.net/modx/wordpress-integrator.html 3-2. make a document which should be the "interface" of WPI. (ex. id=200)
3-3. copy the snippet and name WordPressIntegrator. WPMODX_WP_PATH should be the absolute path of your WP. WPMODX_TITLE is your blog's title.
3-4. write [!WordPressIntegrator!] in document(#200).
If you would like, add [!WordPressIntegrator?block=latest!] in top page, and [!WordPressIntegrator?block=sidebar!] for sidebar.
3-5. make a plugin named WordPressRouter and check "OnWebPageInit". PAGE_WP_TOP is your interface-document's ID. (200 for the example above).
WORDPRESS_ALIAS is the alias to snach from MODx. (wpi_blog for the example above)
note that
http://example.com/wpi_blog/ should NOT exists (oftenly, problems are caused by WordPress placed in
http://example.com/wpi_blog/.
please upload WordPress in another path, like
http://example.com/wp/)
3-6. login to WordPress admin page (Options>>General). set "WordPress address" to
http://example.com/wp/,
"Blog Address" to
http://example.com/wpi_blog/. Uncheck gzip option.
3-7. WordPress modification. replace all "&=" to "=" in wp-settings.php
3-8. You can use [+wp_title+] or some placeholders in the document.
4. Known Problems and Solutions
Q. [!WordPressIntegrator?block=latest!] in the top page works, but the "interface" page does not.
A. Something is wrong about the plugin.
Q. I would like to use alias path
A. patch at here
http://nanabit.net/blog/2006/12/19/alias-path-like-handling/ would help. (still ensure alias path is off)
It makes MODx generate path like alias path, and recognize URLs more flexiblly than alias path.
Moreover, directories' URL will be like
http://example.com/directory/ instead of
http://example.com/directory.html Q. It doesn't work anyway!
A. Probably Ditto2 or Jot are easier to use. I would like to try them, too.

Thanks.