Jeff-Net has released a free Edition of Report Runner viewer.   It is completely free, can be installed as many times as you like and doesn’t have any ads.  It is only missing 2 features that are included in their paid edition:

1) You can’t launch reports from the command line (batch files).
2) You can’t customize the interface

But otherwise it can do everything a report viewer should do (preview, print, export, refresh, etc).  To get your license you have to provide a company based Email address (not Hotmail/Gmail/etc.).  That’s it.

If you want to compare the features of Report Runner with the other free (and paid) viewers you can read my review of Crystal Reports Viewers, which I update every September.