Never ever does a lack of response mean 'I can use this because they didn't say I couldn't'.
Instead of using it, you should probably try finding a free (as in free to use) alternative. As in, spend your time looking for something you can use, instead of waiting for the company to reply that you can use what you wanted. If you look hard enough, you may find something better (or as good) as what you can't use, and you can avoid the hassles altogether. If a company doesn't respond it's probably a 'no', or a 'we didn't see it yet'.
In short, it's always a NO unless specifically stated otherwise. No assuming.