No, it doesn't say that Linux Journal itself is an ‘extremist forum’. It says that TAILs is “advocated by extremists on extremist forums”, and includes Linux Journal as a source of information about TAILs, neither of which seem surprising.
The article, which presumably was written by the authors on its byline rather than by the NSA, says that. The actual config file, linked from the article, at http://daserste.ndr.de/panorama/xkeyscorerules100.txt says:
/*
These variables define terms and websites relating to the TAILs (The Amnesic
Incognito Live System) software program, a comsec mechanism advocated by
extremists on extremist forums.
*/
Linux Journal is listed there, as a ‘website relating to TAILS’, not as an ‘extremist forum’.
