OPEN GTS=OPENGTS is the only FREE solution for AVL, etc.. Wialon, Franson GPSGate Server are leading commercial analogs to OpenGTS.
I use OpenGTS and happy with it. But it is a little buggy and limited in functionality compared to commercial analogs.. The only exisiting c/r*a*c*k for commercial AVL SERVER (do no mix it with client software like Aspicore and others!!) is Tracking Server from ESRI.. You can get it at gisarea.com.. Take care