Hmmm, filters are plug-ins so maybe the free PSPI plug-in for Gimp would allow you to utilize PS plugs in Gimp? You wouldn't know if the PS plug-in were compatible until you tested it, so there is the risk of wasting money. Anyway...

http://graphicssoft.about.com/od/gimptutorials/ss/Photoshop-Plugins-In-Gimp_2.htm