Well, that really depends on the country You live in.
You should either hire or be hired by the people you are working with, or make other type of legal agreement at the beggining of development.
Otherwise, You’ll never know how it will end up.
e.g. without an NDA, there is no protection against leaks, and worse - against stealing source code.
You should never work on a comercial project with a so called strangers, and never without legal background. If you are working without any contract, then people are more than welcome to steal your hard work.
If the project was planned as non-commercial, then probably it shouldn’t be published as a commercial product. Without planning it from the very beggining, it will be really hard to value each member’s work and pay them accordingly.
Basically, making money with strangers is always a bad idea 
And man… I won’t even start about taxes…