The recent switch by Linden Lab to an updated set of tools for building the viewer (which are also being adopted by active TPVs) has meant that as viewers built using these new tools will no longer install on either Windows XP or versions of OS X below 10.7.
Given that neither Windows XP or version of OS X below 10.7 are regarded as supported products by either Microsoft or Apple, the most preferable thing for users on them to do is to upgrade. However, in some cases, this might be easier said than done. To help users who might, for whatever reason, be unable to upgrade to a later version of their OS in the short term, the Lab has issued an “obsolete platform viewer” into the viewer release channel, which will be provided for as long as is reasonable – but not indefinitely.
Version 18.104.22.1680847 of the viewer (dated May 8th although it only appeared in the release channel this past week), is a “static” viewer, meaning:
- It will not receive new features or bug fixes
- It will not be promoted to release status
- It does not change the Lab’s support policy on Windows XP or versions of OS X below 10.7, and is purely – as noted – an interim offering to help people.
The viewer is based on the April 2015 maintenance viewer release (version 22.214.171.1240636), and so includes things like the unified snapshot floater.
Given it is offered only for as long as is reasonable, it should not be relied upon for long-term use, but rather as a means for those who prefer the official viewer and who use Windows XP and older versions of OS X to continue to access SL until such time as they are in a position to update their systems (or the viewer has to be withdrawn from use).
As per all the alternate viewers offered by the Lab, the viewer is listed on the Alternate Viewers page of the SL wiki, or you can use the direct link given above to view the official release notes and download options.