When someone asks a valid question, and I know there's website/webapp that fulfills all or at least majority of the requirements, should I answer with that? On the other words, is it forbidden to answer with website that answers the question?
This meta question is remotely related. For questions, it might be important to define difference between website and webapp, as we probably don't want to have endless stream of questions like
What is good source for this type of news? Are there blogs similar to X?
However, in my opinion, we should define the scope of this site primarily through questions, and not through answers. There's always implicit statement: "I'm asking for software recommendations", so Stack Overflow style answers ("take a look at this library, and write your own program this way") are not a valid (but it could be a good comment, if no answer is found). If the scope is defined primarily through questions, almost everything that answers the question should be acceptable.
Case in point: this question and my answer. Some notes: so far that is the only answer. In my opinion, it is better to have a functional - even if not perfect - solution than nothing. On the question, it is already noted that
most likely it will be a webapp
Another example, created as a better example for this question: this question and this answer. Notes: question does not specify why digits are required, but that those should be calculated. So it's clearly software recommendation question, instead of just "give me resource for...". Also, no operating system is specified.
IMdba webapp and the discussion with @Enjabain brought me to further clarify where the line is between webapp and website. I added a new criteria to the answer you linked. #7: Given you had the program of that thing yourself and would run it on your own server without any data from the original source, the program would still be useful.