If you make a Star Trek fan film, feel free to make a profit from it, but be obligated to give CBS a share of the profit.
You can't make any profit from it unless you specifically have a legal agreement with CBS to do so. CBS is not going to have the blanket policy to let anyone make a film using their property and just give them a set share of the profits. To do so would cause more legal nightmare for CBS than you can possibly imagine, not to mention multiple union violations etc..
If CBS liked a fan film and wanted to use it for a series, they would have to buy it and have everything completely re-shot under there controlled (and union'd) conditions. CBS can never officially support any fan film.
Yes, that is the situation right now. I made "how it should be" statements.