Not really sure what that "-or-" replacement is all about... for SEO purposes, it shouldn't be any problem though.
As for the XML Error: Lack of a XML file and the disorganization of the zip is the problem. Here's the fix and I'm also going to upload the file:
1.) Download another Language Pack from Joomfish. Choose the English pack which is located here: http://joomlacode.org/gf/download/frsrelease/10215/39455/JoomFishDutch_203.zip
2.) Next, create a new folder with the name "joomfish_lang_ja_2.0.2".
3.) Inside the new joomfish_lang_ja_2.0.2 folder, create two new folders called "admin" and "site".
4.) Open the English language Pack and copy the "install.xml" file, then paste that bad-boy into your new joomfish_lang_ja_2.0.2 file. You can close the English file after that.
5.) Now we have to head back to the original joomfish_lang_ja_2.0.2 file you downloaded yesterday at: http://www.joomlaway.net/download/doc_details/42-joomfishver202.html
. Take all the text files from the "administration" file and put them into the "admin" folder of your new joomfish_lang_ja_2.0.2 file. There should be 13 text files inside. Path:\administration\language\ja-JP. Do the same with the "site" folder by copying the text files from the /languages/ja-JP, there should only be 2 files inside.
6.) Almost there.... open the "install.xml" you pasted in the new joomfish_lang_ja_2.0.2 folder with your favorite text editor. You need to change the following:
<name>English</name> to <name>Japanese</name>
<tag>en-GB</tag> to <tag>ja-JP</tag>
under the <files folder="admin"> and <file folder="site"> tags, there is a bunch of lines that kind of look like this: <filename>en-GB.com_joomfish.ini</filename>
All we need to change now is that "en-GB" part to "ja-JP" on ever filename and save it.
7.) Lastly, take your newly created joomfish_lang_ja_2.0.2 file and create a zip file out of it. Now your ready to install it through your admin panel on Joomla!
This can work for any language as long as you have all the text file translations.....
I'm going to get in contact with the person who created the original Japanese LangPack to add this file to their downloads section instead of the one they had. Then we should be able to get it posted on the Joomfish language extensions. Hope that helps and sorry for the length of the post.