Demo is interesting, although it nearly always implies limited functionality and/or limited timeframe you can use the software, which may be misleading for some free tiers.
Freeware could be a good term, but wouldn't it still have the same nothing-is-free issue that GP brought up calling it "false and deceptive advertising"? The term certainly doesn't connote the "why" behind the offering
Personally I prefer demo, because it's a demonstration of what you can expect.