Questions on Total Conversion Modding

Hi there, I'll introduce myself as pretty much a complete newb at building games and I won't make any pretense to hide it. For about 6 weeks now, I've found myself obsessed with the idea of wanting to make a total-conversion FPS game based on the FreeDoom engine and sell it for like $3 on a bunch of the indie markets out and about. I'll also be transparent that I'm thinking 98% on ambition alone and what little is left being relegated to rational thinking and reality.

I've tried to do my homework on the subject for a while now, but it seems as though I might get the straightest answers just asking the forum here:

1. Does the GNU license on Freedoom allow me to use its engine as a template to design levels, build new gameplay resources, and edit code to create a game I intend to make (some) money on? A reasonably simple YES or NO will suffice, and if not, I will honor the license and not attempt it.

If yes,

2. Are any of the custom made graphics that I've seen posted here for monsters and weapons (ones not generated/edited from licensed Doom designs) part of any royalty free pack or could be licensed for my use for a reasonable price? I don't know if I want to be bold enough to ask if they're public domain, and even though I am trying to be pretty cheap about this, I will not cheat anyone out of money to get what I want.

I intend to design brand new levels, music, and whatever programming I can do within the engine/template to make this prospective game unique on my own, but the graphics and whether I'm ok to start like this are where I'm having trouble at.

And I'll answer this question ahead of time, "why not just build your own graphics and game and programming from scratch to make it your own?" For the same reason you don't make your own clothes, build your own house or hunt your own food every time a want or need arises. I don't care what tools I use, I just want it to be good and legal.

I think that is all I have to say on my request, as articulated as I could make it. Thank you and I look forward to your guidance as to the feasibility of my quest.

1. Yes - Freedoom's BSD license does permit the sort of changes you wish to make, but there's no engine. It's an IWAD replacement that's intended for use with Boom compatible source ports, at least some of which will have licenses liberal enough to suit your purpose, though you'll have some more research to do.

2. Probably. Best person to ask would be the creator of whichever graphics you're considering using.

You may want to keep in mind that, if you ever decide to credit or mention the game engine you use, say the Doom engine. Obviously Freedoom is a TC in itself!

I like these indies asking if they can use the Doom engine to make games. It means we'll probably see some real FPSes on the market! Not that all FPSes nowadays are bad.

Freedoom has BSD license, but the game engines are either GPL v2 or v3, depending on which Doom port you're looking at... In all cases you can sell the product, but if you make any game engine changes then you're obligated to publish that code. This probably doesn't include scripts that run on top of the engine though, in the case of those that can be scripted - maybe someone can clarify this if you say which port you're considering.

I'd be wary of using random art you find on forums, because much of it is edits of IWAD resources, or even stuff ripped from other games. Everything in Freedoom is totally original though.