It is a matter of perspective to some extent.<p>If what they say is &quot;if you add this extra functionality without our permission, we will sue you&quot;, it is not OK. This cripples peoples ability to innovate.<p>If they on the other hand say &quot;This is the basic functionality, and you can buy this add on package for $400 if you want extra functionality&quot;, I have less problems with it. The latter opens up for third party addons, possibly being more innovative than the original addon software. What I find abusive is the attempts to prevent people form innovate using the law.