Migrating from Joomla or Mambo

This guideline focus to migrate Joomla! 1.0.x to Drupal 4.7.x. Before you do migration you must understand some differences between both to make sure your migration to be successful:
Joomla! vs Drupal

1. Joomla only supports single Section/Category, while you can set same Drupal article has several Sections/Categories.

2. Joomla does not support Community Site, so the migration must be put into certain site if you already set a multi site for Drupal.

3. In this guide I assume you have a forum in your Joomla site. Drupal has built-in Forum Discussion then you don't need to install additional module

4. Blogging. Blog term in Joomla is not same as blog in Internet dictionary. 'Blog' term in Joomla is a list containing: Title, Introduction and Read More link. So, in short, 'Blog' in Joomla term is not 'Weblog'! If one asking if Joomla support Blog by default then the answer is yes, but in Joomla term of 'Blog'.

And you may ask: "I see that Joomla official site supports Blogging! Look at http://dev.joomla.org, am I missing something?" No, you're not miss read! Joomla uses bridge to include Wordpress in Joomla site.

5. Commenting is not available on Joomla by default but Drupal support comment by default.

Joomla vs Drupal Terminology

There are some different term between Joomla and Drupal. Here I listed to give you quick understanding:

1. Template in Joomla is called as Theme.
2. Component = Module.
3. Module = Block.
4. Mambot/Plugin = ? ( I don't know yet!!! )
5. Menu-Horizontal = Primary Links
6. Menu-Vertical = Navigation
7. Dynamic Article/Content= Story
8. Static Content = Page
9. Back-end = there are no back-end in Drupal!
10. SEF/SEO = Clean URL but some docs refer to SEF or SEO too.
11. Section = Category
13. Section Title = Vocabulary Name
12. Category = Sub-category or Term
14. Introtext = Teaser
15. Maintext = Body
16. Pathway = Breadcrumbs

Others parts are same, such as: forum discussion, editor, search, region, comment, subject/title, preview, html tag, view, edit, advertising/banner, log in/log out, profile, avatar, access control, logs, cache, site maintenance, RSS feed, parent-child and snippets.
Migrating Joomla Content/Items

First, you must transfer all Joomla-Sections to Drupal-Categories and transfer Joomla-Categories to Drupal-Term according to their parent. After that, you can transfer Joomla content/item from jos_content table. Drupal table for saving article is drupal.node_revisions. I am using SQLyog (www.sqlyog.com) to Export-Import these tables.
Migrating Joomla Introtext

Introtext vs Teaser, this is very important, you must know that Drupal can automatic cut the beginner of an article to introtext. The introtext is called as teaser in Drupal. Now, how to convert Joomla introtext to Drupal? You have 2 options to solve this problem:

* Automatic Teaser
Just use content=introtext+maintext and save to this Drupal table: drupal.node_revisions:teaser. After the automatic teaser created you still can changing this teaser manually using Drupal tag:

* Manually Teaser
Copy jos_content:introtext to drupal.node_revisions:teaser and jos_content:fulltext to drupal.node_revisions:body

Migrating Joomla Forum

I assume you use Joomlaboard forum for Joomla. In Drupal, forum is built-in, then you only need enable it on administer-module then show it on certain front page section using administer-blocks. You must transfer Parent-Forum Category of Joomlaboard to Drupal-Forum Container and Child-Forum Category to Drupal-Forum Category. Again, I am using SQLyog to transfer the entire forum contents, SQLyog is very easy because its GUI.
Editor

Drupal by default has no WYSIWYG Editor, mean you must type any HTML tag manually to format you article. Joomla has built-in TinyMCE editor. In Drupal, you can use users contributed modules such as TinyMCE Editor or FCKeditor. TinyMCE is light editor. FCKeditor editor support server side, mean you can browse the server to insert or upload something including files, images and flash file. Also, Fckeditor can create folder on the server.
Tips

Usually better to install Drupal in a folder such as domainname.com/drupal, so you can still access both website during this migrating. You better not convert the Joomla templates to Drupal Theme, but edit any existing Drupal theme to meet your requirement because Drupal supports theme engine (PHPtemplate) and separate templates such as comment.tpl.php, mean you can apply any format to the comment.