From a new posting over on Dynamically Typed:

To some developers, one of the large drawbacks to PHP is that it provides no official method for distributing closed-source, binary web applications. Developers of commercial applications often want to keep their source code private, for various reasons.

[...] Some may claim that distributing PHP applications as 'closed-source', in binary form, is a bad thing as it is detrimental to the open source community from which PHP itself comes. However, The PHP Group themselves are happy for PHP to be used commercially - the PHP license is very permissive in order "to help PHP become as popular as possible". I would argue that if being able distribute their applications in binary form only allows more developers to switch to PHP, it is a good thing for PHP.

Of course, it's inevitable that PHP developers out there would want to use products like the Zend Encoder and Turck MMCache to keep their code safe, and there is a certain logic to their thought. I have to agree with the "bad form" camp, though - PHP is all about Open Source, and furthering the cause of the language should be about promoting all aspects of the language - everything from its ease of use to the fact that the source is right there for all to see...