What are the rules in dealing with mnemonic characters (words using the ampersand)
You don't have to use the original mnemonic character in the string. But, before you change it to another mnemonic character, you have to know where the string is being used and check if there are any conflicts.
For example, "&File" is translated to "&Datei" in German. But, before we choose "D" as the mnemonic character, we have to check if it's conflicting the mnemonic characters for "Edit", "Source", "Window", "Help", etc.
Keeping the original mnemonic character wherever possible will minimize the possibility of conflicts because we know (supposedly tested) that we do not have conflicts in English.
Note: even if there are conflicts (2 of the same mnemonics in the same pulldown menu), it's still okay. Most OS will cycle through the choices and highlight the selection when you press the mnemonic again. Of course, it's better not to have any conflicts to avoid confusion.
How good are the Babel community translations
From what the Babel team has seen so far, the quality of the Babel community's translations is quite high. Many translated strings were done by professional translators, and their work has been donated to the Babel project. Babel also has Language Champions which help oversee the translation efforts.
There are plenty of translation tools. Why did Babel reinvent the wheel?
Although some may assume Babel has reinvented tools like gettext, we haven't. Babel starts with strings that have already been externalized. When Eclipse projects haven't properly externalized their English strings, they cannot use the Babel community for translations... See https://bugs.eclipse.org/bugs/show_bug.cgi?id=241848 as an example.
The scope of Babel is to leverage the community to translate those externalized strings. The web UI translation tool (at http://babel.eclipse.org/) started with a code contribution from a company called Aptana, so again, we're not inventing any tools here. We have taken the tools that have been donated and we're are evolving them.
Have you considered sharing your work for other translation attempts?
Others are free to consume our translations by downloading the NL fragments, and others are free to download and use the web-based translation tool we're working on, as it is in CVS: http://dev.eclipse.org/viewcvs/index.cgi/org.eclipse.babel/server/?root=Technology_Project