A key point to be aware of when talking about freedom of speech is that it does NOT grant anyone the right to have a media outlet publish something on demand.
An example would be to send an article about a favored topic to the New York Times and demand they publish it on the front page above the fold. You'd not even get a response from them. Much less your article printed. It is their paper and they get to chose what gets published.
It's the same with online forums. Someone owns the outlet and they get to chose what stays or does not. This in no way violates anyone's right to free speech.
Want to say something online? Create your own web site and spout off all you want about anything you like. That is your free speech right.
It is great that you are a loyal customer and feel strongly about the UBBThreads product. Please consider the potential disservice to the product via negative attitudes some might develop from the perception of spamming.
As Rick said, there is a cottage industry where companies will spam forums for a product. It's called "Shilling" and is generally frowned upon to put it mildly. To be perceived as a shill for a company is to make people think the company stoops to such business practices.
I for one do not support such companies and will not purchase their products. Not all I am sure, but others feel and act the same.