The VG Resource

For a long time now, I've seen this being discussed in the comments section of games that are not considered "official". I am probably guilty of starting this trend of just tagging everything that isn't licensed as "bootleg", and I really need to sort of educate everyone what exactly is the difference.

Bootleg
A bootleg game is an unauthorized port of a game to another console, an unauthorized romhack of a game that was distributed illegally, or a completely original game that is stealing assets from something else.

https://www.spriters-resource.com/nes/rollingthunder/
This is an illegal version of Rolling Thunder for the arcade, ported to the NES without Nintendo's permission.

https://www.spriters-resource.com/nes/po...owbootleg/
This is a romhack of Felix The Cat on NES, replacing it with Pikachu. This was distributed on Famicom cartridges illegally throughout Taiwan and possibly Russia.

https://www.spriters-resource.com/nes/po...erbootleg/
This as far as I'm aware, is a completely original game but is using copyrighted characters without Nintendo's permission.

Unlicensed
An unlicensed game is simply put, a game that was developed for the console but was not given a license by the console's holder for various reasons.

https://www.spriters-resource.com/nes/raid2020bootleg/
One of Color Dreams' many infamous games, possibly not licensed because it doesn't meet Nintendo's quality standards (whatever those may have been at that time)

https://www.spriters-resource.com/nes/rockballbootleg/
A game made by a Chinese company that was produced possibly long after the initial run of the Famicom.

https://www.spriters-resource.com/nes/qu...odbootleg/
A game developed by Code Masters who presumably did not want to pay the license fee but still wanted to distribute their games.

https://www.spriters-resource.com/nes/linesbootleg/
An unlicensed game made in Russia somewhere in the 2000's, again long after the Famicom's original release.

Hacks
A hack is a modified version of a game's ROM or ISO, changing of the graphics, sound, or even gameplay entirely. Hacks are usually not sold within mass markets unless they were added to a pirated game system.

https://www.spriters-resource.com/nes/th...enderhack/
A romhack of Wolverine where you play as... the LJN Defender? Beating up the Angry Video Game Nerd!?

A big question that some people may ask is where Action 52 falls. The games were original (although inspired by some games) so you may think it's simply unlicensed. That isn't totally the case though, because some of the music was actually stolen from an Atari ST game called "The Music Studio"
Therefore, Action 52 has plagiarized content in it, making it a bootleg.

I'd add Homebrews to this list too.

This is a really tricky subject and the rules aren't really listed out anywhere. I hope to address this in the future.

Yeah homebrews are definitely their own category. Homebrews are made by independent developers (or sometimes by a small team) who wanted to either experiment with their developing skills or breathe new life into their favorite consoles.

Where would "mods" fit in this list? (I'm thinking stuff like Project M)

Games like Street Heroes (NES fighting game by Sachen) are pretty interesting cases too, since it normally doesn't seem to use any outright copyrighted content, but resetting the game changes its intro and title to that of a Samurai Shodown game.