Appropriate credit of remixes...
I've produced an improved (IMHO) XL Spool Holder. Initially, I tweaked the Prusa STL's but then found it easier to created my own models in CAD and borrowed some the object dimensions from the original. When does one 'cross the line' from remix to original creation? Regardless, I wouldn't claim I dreamed up my version on my own (it's pretty obvious it isn't). Just curious.
RE: Appropriate credit of remixes...
There's no clear line in the sand. Many times I see something interesting but want to tweak it. More often than not I find it easier to just reimplement the model in CAD to make the changes. In those cases I label my reimplementation as a "remix", to give proper credit to the individual who came up with the original idea.
Formerly known on this forum as @fuchsr -- until all hell broke loose with the forum software...
It is impossible to patent an idea ... this is a good grounding on which to decide originality:
If you thought up and created your own, novel, invention then it is clearly your own, original work.
If you were told about, or saw, an object then decided to create a similar item from scratch, or better, an improved version from scratch, then it is your own original work. It would be polite to acknowledge the source of the idea but not mandatory.
If you used any original part of a previous work to create your work (including computer files) then it becomes a derivative (original part:- something created by the previous designer, not a public domain part - so you can copy an M8 threaded hex nut with impunity but not the whole robot.) To publish or sell a derivative work you must read the (perhaps implied) license and behave accordingly; if you want to do something not permitted by the license then you must contact the license holder, usually the original designer, and ask/buy/negotiate permission.
If you reverse engineer a part and reproduce it then that too is derivative, as also is a cast of an original, or a scanned print.
Be cautious with the licence of your design software, if you use a part from a library supplied with it that might make your work derivative.
If you create something to attach to some commercial object then be careful, in some cases the connection profile may be copyright so that part of your design may be forbidden; but copyrights expire in a few years so you might just have to wait a while.
If you create an original work but then pretend it is someone else's work (Rembrandt's 'Portrait of the artist as a plastic robot'; Tesla's petrol filler cap.) then it is either passing off or forgery, you had better have good lawyers. Companies ger particularly annoyed when someone makes an inferior part and sells it cheap causing unwitting customers to contact them with warranty claims on something they didn't make. There are thousands of items on Printables that carry copies of commercial trademarks and logos, in theory all of these could wind up in court.
...but copyrights and patents are time limited. Depending on the type of work and which country's juridiction applies it may be a dozen years or over a lifetime so eventually everything becomes available.
Cheerio,