Pretty much anything will be legal if you don’t release it, though in any case it’s also good to distance yourself from IP (Intellectual Property) as much as you can.
Make everything from scratch (not just code), use different names, don’t look at their version after you started (no side-by-side), and add your own ideas/changes. Don’t even reference terms (particularly on a release page) related to the original, and don’t release/announce/tease anything until it’s done (a DMCA can stop your project in its tracks, but if 100+ people already downloaded it likely cannot be stopped).
Note that I’m not looking into making a product, just learning
Pretty much anything will be legal if you don’t release it, though in any case it’s also good to distance yourself from IP (Intellectual Property) as much as you can.
Make everything from scratch (not just code), use different names, don’t look at their version after you started (no side-by-side), and add your own ideas/changes. Don’t even reference terms (particularly on a release page) related to the original, and don’t release/announce/tease anything until it’s done (a DMCA can stop your project in its tracks, but if 100+ people already downloaded it likely cannot be stopped).