Okay, so I actually found the place in the software license where it stated the only thing I could find that might be similar;
"You agree not to otherwise reproduce, copy, modify, decompile, disassemble, reverse engineer or create derivative works of any portion of the Application and Data, and may not transfer or distribute it in any form, for any purpose, except to the extent permitted by mandatory laws."
The application refers to the interface, garmin software (the gps itself), and the map data. The map data is actually third-party information that is licensed, not sold, to Garmin. So I think as long as you aren't trying to reverse engineer those copyrighted maps/ interfaces and/or trying to sell or redistribute them, you are fine. I have gotten numerous accounts of confirmation from Garmin that third-party maps are allowed. I even found an official article instructing you how to properly download third-party maps -- which requires putting those maps into the .img format in order to enable/disable them.
So unless I've missed something, I think we're okay. Any outside comments are appreciated.
I actually just got confirmation from a Garmin tech support employee myself, so I think we're doubly okay. I'll attach the screenshot below. If someone can confirm that I asked the right questions, I think I can rest easy for real.
I've been told that I just can't legally copy or reproduce garmin-branded maps, but third party maps should be fine. Garmin supports the use of custom maps on their devices, right? The .img and .gmapi format doesn't seem wholly unique, either, though I cannot confirm that. I can't seem to find anything online that contradicts this, either. Nothing pops up that tells me it's illegal to do. But I get worried about this stuff, so any further comments are welcome. Thank you again.
Alright, I see. I suppose it's mostly a question of ethics, then. I looked at the maps from Garmin, and they are... well, a tad overpriced, to say the least. I know most the maps on this website were created using legal means, through programs like OSM. I think that's what my main concern was. This probably shouldn't bother me. I don't know -- if anyone has any good insight on this, please let me know. I appreciate your response, kind person.