Software Development en Barcelona

I am developing a Cloud Storage service similar to Dropbox or Mega. I would like to find contributors who would be remunerated in an original way: they will get by contract a percentage (to be negotiated) of the incomes generated by the software.

Strictly speaking it won't be a labour contract but a merchant one. Depending on your country of residence it could have different legal connotations. You should study the legal connotations by yourself.