Yes. But its nowhere near as powerful as capabilities.

- Pledge requires the program drop privileges. Process level caps move the "allowed actions" outside of an application. And they can do that without the application even knowing. This would - for example - let you sandbox an untrusted binary.

- Pledge still leaves an entire application in the same security zone. If your process needs network and disk access, every part of the process - including 3rd party libraries - gets access to the network and disk.

- You can reproduce pledge with caps very easily. Capability libraries generally let you make a child capability. So, cap A has access to resources x, y, z. Make cap B with access to only resource x. You could use this (combined with a global "root cap" in your process) to implement pledge. You can't use pledge to make caps.