How legal is relocation to Poland through incubators?

Question

Emigration and immigration

I am considering the option of relocation to Poland through https://mojafirma.org/, that is, I will formally work for them, they will provide me with an invitation to work and all that, but in fact I will receive money from clients to myself and transfer their companies, and they I will be “paid a salary” with this money.
It seems to be a common option with Poland, but how legal and / or risky is it?
If anyone has experience with such companies, please share your experience.