[JKT]

You can download the app but it is limited to the number of items you can use (20 I think). If you open a previously created document containing more items than the limit, it will still open but it will be read-only. However, if you go to the OmniGroup store, you can obtain free 24 hour licences to test out their apps in full (you can use as many of these as you like within reason, so long as they don't run on concurrent days - I think there has to be 36 or 48 hours between the expiry of each 24 hour licence).

Installing the latest version will not overwrite the old version and you can use them side-by-side if you want to. Just be sure to save modified files as new files rather than overwriting so that you can revert back to 4 without any issues if you need to.