Are all messages posted on the platform free?

Yes, if I understand correctly, all messages are absolutely free.

how then will the developers earn to maintain the operation of this platform?

probably they find other sources of income for the development of their platform.

today the platform is already in working condition, so I think that the team no longer needs additional investments.

but investments are needed to maintain good platform performance, and we are interested in where they take them.

maybe the team is collecting any donations?

Perhaps, but personally I have not seen any information about this.

probably this is the same secret as those left by users on this platform))