It is a permanently free version. You get 40+ pieces of gear and about 100 presets forever. No time limit. You only pay if you want to unlock expansion packs (like the Fender Collection or Orange amps).
The secret is simple:
The free version of AmpliTube 5 comes with , which form the basis for several dozen factory presets. Included Gear : amplitube 5 presets list free