I studied your Simple Machines Forum a bit and it seems to be a really nice piece of software. I understood that it would be legal (according to the license) to build a service on top of the SMF since the actual software is not distributed in any way. The reason of this post is to make sure we understood the license correctly; so is it legal to modify and build a service - even if it might become commercial at some point - on top of the SMF, when the actual software/sources are not distributed forward in any way?
Thanks in advance.
I can create a PHP application that integrates to SMF. I can modify any of the SMF files while integrating it. When I want to distribute my application, if the installer doesn't have any core SMF files in it (modified or not), it is legal to distribute. I can also set a price for the application.
So yes, you are allowed in your condition.
Note that it is illegal to redistribute individual SMF files, as well as the whole package. You are free to distribute modification packages, however.