MyBB Community Forums

Okay my current set up is the forum is on the main index page:
http://yoshistr.com/index.php or www.yoshistr.com

What I want to do is make my main page a full website then move the forum to a subpage, if it makes it easier I can leave it in the same directory:
http://yoshistr.com/forum.php

How can I do this without making a huge mess in the file system/database?
So I can have a custom index page for my site with a link to the forums?

in .htaccess

DirectoryIndex main.php index.php index.html

then you can create a main.php for your full website main page

http://yoursite/ will show this main page

http://yoursite/index.php will be your forum

this is the only way to do it without code changes in MyBB that does not break the breadcrumb links, location in who is online, etc.

otherwise renaming index.php to forum.php also requires you to change index.php to forum.php in the actual source code, and you have to reapply these changes with every update...

How can I move it to say http://yoshistr.com/forum?

http://yoshistr.com/forum or http://yoshistr.com/forum.php ? There is a difference.

To a different directory called forum within the main directory.
I'm trying to avoid using htaccess file editing because some SEOs don't recommend it.

If you use a 301 redirect for any redirections you shouldn't have any SEO problems.