Heh? Prior to the apps, you used to get the software for free (when you buy the box, you had the right to download the software). It wasn't until iDevices that sling started charging anyone for their software.
The Slingplayer software was only free for the desktop. For mobile devices, it was always around $30. (There were trial versions as well, and some boxes on sale might've come with a coupon. Perhaps you had one of those?)
The good news was that you could buy a player license and transfer it as many times as you wished. I started using Slingplayer on one old Windows Mobile phone and upgraded to new phones several times over the years.... and just kept using the same license code. (When you activated the player on the new phone, it registered it with SlingMedia, and the old one stopped working.)
I did have to buy a separate version for a non-touchscreen Windows Mobile phone which had no carrier plan. That's the device I used around the house and yard over WiFi as a handheld TV.