First of all, I'm not looking for miracle... I know how PHP works and that there's not really way to hide my code from the clients without using encryption. But that comes with the cost of an extension to be installed on the running server.
I'm looking for something different though... I'm not looking to encrypt my code or even obfuscate it. There are many PHP scripts without encrypted/obfuscated code but they are commercial applications. For instance, vBulletin and/or IP.Board forum applications.
I just want to know what approach do these guys use for their applications...
I'm also open to any other suggestions.
Please note that I'm a single person and not working for a company. My product is also very specific, it won't sell that much. I just want you guys to know that I can't afford to consult a legal professional either to sue someone or prepare a commercial license. I'm just looking for a simple way to protect my simple product, if it's indeed possible, somehow...
Obfuscating things can only inconvenience your legitimate, law-abiding customers, while the people who would would rip you off are not your target paying customers anyway. (edited out other thoughts about obfuscation)
Another suggestion for protecting your software: create a business model in which the code is an incomplete part of the value of your offering. For example, sell product licenses along with access to some data you manage on your site, or license the product on a subscription model or with customer support.
Designing a EULA is a legal matter, not a coding matter. You can start by reading some EULA text for products and websites you use. You might find some interesting details!
Creating a proprietary license is is highly flexible, and probably a subject beyond the intended scope of StackOverflow, since it's not strictly about coding.
Some parts of a EULA that come to mind:
You should consult a legal professional to prepare a commercial EULA.
edit: If this project can't justify the expense of a lawyer, check out these resources:
You need to consider your objectives:
1) Are you trying to prevent people from reading/modifying your code? If yes, you'll need an obfuscation/encryption tool. I've used Zend Guard with good success.
2) Are you trying to prevent unauthorized redistribution of your code?? A EULA/proprietary license will give you the legal power to prevent that, but won't actually stop it. An key/activation scheme will allow you to actively monitor usage, but can be removed unless you also encrypt your code. Zend Guard also has capabilities to lock a particular script to a particular customer machine and/or create time limited versions of the code if that's what you want to do.
I'm not familiar with vBulletin and the like, but they'd either need to encrypt/obfuscate or trust their users to do the right thing. In the latter case they have the protection of having a EULA which prohibits the behaviors they find undesirable, and the legal system to back up breaches of the EULA.
If you're not prepared/able to take legal action to protect your software and you don't want to encrypt/obfuscate, your options are a) Release it with a EULA so you're have a legal option if you ever need it and hope for the best, or b) consider whether an open source license might be more appropriate and just allow redistribution.