The "official" reply is pretty much the same as Ciege's:
There is no separate installation package for the Ranorex runtime, nor for the trial. The installation package you get for the "trial" download is the normal Ranorex setup, containing the fully-functional Ranorex software. The installed license decides which parts of the software (Ranorex Runtime, Spy, Recorder, Studio) you can use on your machine (see http://www.ranorex.com/product/editions.html
If you don't install a license, you have 30 days to try out the complete Ranorex software, i.e. all parts mentioned above. Consequently, there is no downside of using the "trial" setup to test Ranorex runtime. The only thing that you won't get when a runtime license is installed (apart from the ability to start Spy, Recorder, Studio) is the nag-screen coming up every time you start an executable
If the nag-screen is a problem for your test, you can also contact sales_at_ranorex.com and ask for an extended-trial-key.