I would assume that you need the GL-5 fluid in the transmission since it is a newer vehicle. GL=4 requirement was for specialized transmissions with brass syncronizers (such as the new Venture Gear 4500 5 speed). I have never had a problem using "Royal Purple" oil in any transmission regardless if it needed GL4 or GL5. The harder you work the transmission, the better it ran!
Top of the transmission...
The 2014 Volkswagen Jetta has a 5-speed manual.
The 2011 Volkswagen Jetta has a 5-speed manual.
The 2010 Volkswagen Jetta has a 5-speed manual.
The 2004 Volkswagen Jetta has a 5-speed manual.
The 2006 Volkswagen Jetta has a 5-speed manual.
The 2005 Volkswagen Jetta has a 5-speed manual.
The 2012 Volkswagen Jetta has a 5-speed manual.
The 2001 Volkswagen Jetta has a 5-speed manual.
The 2008 Volkswagen Jetta has a 5-speed manual.
The 2013 Volkswagen Jetta has a 5-speed manual.
The 2009 Volkswagen Jetta has a 5-speed manual.