Maximum members

I have a question, is there a limit on members for the boonex platform ?

No, any limit would come from your server configuration such as running out of space on the server.

It also depends on how many sites are hosted on your  shared server. If there are couple of busy sites on the same server, then as you grow in number of members , your site will slow down tremendously .

I suggest after 1000 members you get a dedicated server.