> Open Source software... where deliberate hobbling is not possible
Actually, it is. If the agreement you have committed to with a supplier includes limitations on the "what, how, when or how-many" you are permitted to use, it makes no difference whether you are physically or logically able to enable those features that you haven't paid for. Or whether any software that comes with (or forms) the product is Open Source or closed source. You know: all thise "I agree" boxes you tick. They can contain any limitations the author wishes to include.
Even if the software comes with its source code, if you contravene the terms of the purchase / rental / usage then that is as much a no-no as if you'd cracked any protection schemes that prevent a user from access those additional features. Though with "free" software, this is mainly down to the honour of the user - to abide by the terms they agreed they would, than hard prevention.