In my search for information about language packs and it's availability for MOSS 2007, I came across the SharePoint team blog posting about this subject... I've somehow missed it before... :)
Anyway, very useful information for some of our customers that are going to be dependant on (Dutch) language packs. From the article:
"Language packs are available to install on WSS only, MOSS, MOSS for Search, Office Forms Server, and Project Server installations. For MOSS, MOSS for Search, Forms Server, and Project Server installations, the Office server products Language Pack (a.k.a. ServerLanguagePack) needs to be installed; this will take care of all sites. The WSS Language Packs (a.k.a. SharePointLanguagePack) are for WSS stand-alone installations.
Microsoft’s 2007 Office server products are localized into languages in two different ways: 1) fully translated SKUs and 2) Language Packs. A language-specific SKU delivers the respective Office server product localized into a given language. A Language Pack may be applied to an installed Office server product to create sites or site collections in other languages. Application of a Language Pack will not change the language of the installed Office server product SKU.
To download the Language Packs for Beta 2 or very soon for Beta 2 TR, go to http://www.microsoft.com/office/preview/beta/download/en/default.mspx.
See Deploy Language Packs in Office SharePoint Server 2007 for more information on how to install the language packs.
NOTE: The English Language Pack will not be available as a single language pack. You may install the English Language Pack when the Multiple Languages Language Pack (which includes all languages) ships."
Read the full article about which language packs for what version are available.