The time limit varies from platform to platform, but always averages out at around 90-100 minutes, equating to around 5 in-game days. To ensure this isn’t exploited, you have a time limit imposed once you begin the trial. The free trial (regardless of the Edition or your platform) is the full game as paying customers would experience it there is no barred content that will be inaccessible.
In terms of the Java Edition, which is available exclusively to Windows, Mac, and Linux, an additional set of links are available lower down on the same page, with specific instructions on how to download and install each respective version.