I think this is a case where the most "optimal" technology is not necessarily the best. I'm sure XSTL can be very useful but maybe simpler editing by everyone is more important (if such a thing exists).
In any case let's not dump alternatives immediately. First and foremost comes the planet website (in parallel with set-up of association), once it will be up it will be easier to decide I hope.
Everything that has been said here it's really interesting!
This is just my two cents:
have you considered joomla?, we could create a template that suits the clean face of GGL, there are at least two important components we could use:
1) Caching, as most of the site doesn't change, this could help reduce any overload it may cause.
2) This one is really important, there is a component called JoomFish that we could use to manage the translations
The key features of the fish are:
* Possibility for an unlimited amount of languages
* Possibility to MANUAL translate all dynamic content of your Joomla! installation in ONE database
* Overview of the changed contents in the Translation list
* Support for all the core components/modules of Joomla!
* Frontend component for language selection
The United Nations have been using this combo in one of their sites.
(I know that URL looks awful to search engines' eyes, but we'd activate the Search Engine Friendly URLS option)
About SVN and tracking system: I'd go with Trac, I think it's better to use a tool that does one single thing really good (by this I mean tracking the progress of the creation of Planet GGL).
Yes Joomla is being considered too. Caching is a requisite anyway (by nature it's a static site), and the capabilities of the JoomFish module are very interesting. As for readable URLs, it's difficult to set-up (last time I looked for the translation wikis, instructions looked just as bad as my latest organic chemistry exam) but possible.
My biggest worry, however, is the complexity of setting this up on different domains. Indeed, the Spanish translation will switch to obtengalinux.org very soon thanks to Gustavo; the French and upcomming Catalan translations will probably have their own domains soon too. I intended to announce this officially but was caught short :-) We shall see very soon about what to do, when the planet is up.
Speaking of the planet, anyone have a peek into the work in progress with "curious" as username and password, it is progressing slowly but steadily. The project management is up and running and you can login with the same user&pass. SVN is now used for the Spanish translation and as soon as I get around to learn to use it the English French and Catalan versions will be in it too =)