Rummi is not free software; you need to buy a license if you want to play the game.
Before spending money, you can try Rummi out for free and see if you like the game. In evaluation mode, you can play the game and fully explore the software, with the following limitations:
You can play for 15 days.
You have 15 days to evaluate the software. These are days of real usage; if you don't use Rummi for a day, then that day won't count.
After 15 days, you must either buy Rummi, or remove Rummi from your computer.
Nothing is saved.
You can build up a game score, add new players, define your own games, etc.. But when you close the Rummi window, everything will be lost, and the next time you'll start all over again.
No private online games.
With an evaluation membership you can play online, but only on public tables, not private ones.
These limitations may change in the future, even for existing evaluation members.