We live on a race for extinction of wild places. The tradeoff of supporting local inhabitants vs purely hard green preservation is a neccesity for the survival of both. Sirena is a perfect example where you just need to read Tico Times of any other newspaper to inform yourself of the many things going on the backstage. That the park itself remains open to the public will rely mainly on what tourist do while they are there.
Corcovado Adventures (the formerly known Corcovado Tent Camp) needs no introduction as having pioneered ecoturism in the Drake Bay area it will be more than enough to say that Dña. Yessica, Dña. Karina and D. Gabriel, the people behind the Good Old Tent Camp, running under refurbishment these days, are the driving force under the hood of Dreams Corcovado.
Make yourself a favor and, if you plan of following the rules (basically the John Muir's "Leave no trace"), don't miss the opportunity to book with them. If you think on going like if you were to a dump site leaving tissues as you go or harrassing guides to get the tapir to bow before you, there are plenty of spoiled places out there to choose instead of this one.