We fail to get CategoryTree to work with mw 1.20 and see no documentation that a specific older version should be used.
Failing: http://biowikifarm.net/test_v20/Category_Test - this should look like
http://biowikifarm.net/test/Category_Test (the latter still under 1.18.x)
See here for other installed extensions: http://biowikifarm.net/test_v20/Special:Version
This seems to be related to the discussion
http://www.mediawiki.org/wiki/Extension_talk:CategoryTree#no_categories.21_20941
where others seem to have similar problems with mediawiki version later than 1.18.
Version: REL1_20-branch
Severity: critical