It just needs to be a set of instructions. No need to make a business out of it. Could be hosted on Github/Gitlab or pretty much any other collaborative version control system and the design could be documented in Lego Digital Designer or similar programs. Of course the real thing probably would be better made out of special purpose parts but Lego would still be a good starting point for many experiments.
Edit: point out that I realize Lego is not the best long term platform.
Edit: point out that I realize Lego is not the best long term platform.