The same as Windows, start it with the -logging argument, like:
Add -stats if you want csv output as well.
Now about the message you're getting, I'll go into a bit more detail. It means there has been a problem retrieving messages from a certain instance of poclbm. During normal operation this can happen when switching pools. It says terminating because it stops the poclbm process and then restarts it. Usually, the method that reads poclbm output will just return null when the process is stopped and re-started and it always does so on Windows, but not on Linux. On Linux it sometimes throws an unhandled exception that causes that message to be printed when the process is killed, but this is not necessarily a problem. So if you're getting those messages when switching pools and all your GPUs are still active I don't there's anything for you to worry about.

@ampirebus As far as I know bclc delays stats, don't they? I'll see to the JSON problems, but I wouldn't exclude the possibility of them intentionally messing with stats either. However, since nobody else mentioned a problem with them, are you sure you were mining there at all?