So, I'm trying to interface my https://isptriage.com app with a PBX system, and like FusionPBX's overall functionality... it mentions API details but gives no information on the use of it, why? And does anyone have any details on this?
Well you're getting fusionpbx free so why not pay for additional features. You're making money from it so why shouldn't the developers.
And if you want to provide a product to paying customers it's prudent to have expert support should you need it.
We are currently developing the API. It should be released soon. FS PBX is a forked FusionPBX with lots of additions targeting specifically external integrations