On an test website with Joomla! 2.5.11, SEF and few other plugins I first installed "Glossary 2.8".
It works, but I did not like it. So I disabled it for the moment, looked for an alternative.
I tried Gnosis, started with version 1.0.9.
In the administrator interface I went to the component menu, had the Gnosis line with two (1.09: not quite correct) menu items.
Both menu items gave white screens only when clicked.
Thus I installed 1.0.b7 and later 1.0.6; these two had the correct menu items, but did not give anything better, just white screens.
Before each install I tried to remove all of Gnosis; Gnosis Package cannot be removed in the extension manager, it gives an error message like "manifest file cannot be found".
Furthermore I spotted a typo (compnetn instead of component), not important, see screenshot.
Yes, the test website has the latest stable Joomla! Version, i.e. 2.5.11.
(the productive site is www.dampfzentrum.ch).
Too bad if I cannot use Gnosis on a site with the stable version - I will wait for Jomla! 3.5 before trying an upgrade.
May be I will give it a try with a 3.0 site, once I get round to install such a test.
Maybe when I get a stable version of Gnosis I can look into converting it to Joomla! 2.5. Right now though, I don't have the resources to handle two separate packages. My intention with Gnosis is to add native Joomla! tag support, 2.5 just does not have the tag system. Also, 3.x is the future of Joomla!, and since there isn't another freely available glossary component for Joomla! 3, and I needed one, it seemed to be a good place to start.