I also concur that this case clearly falls within the scope of marketing/product-placement.
The use of an advertised product (Astah) - might actually be an appropriate response to a given question and doesn't necessarily warrant a flag. Especially if the poster is going into enough detail in explanation and thoroughness with how the product meets the OP's described problem.
THAT BEING SAID, I believe that the community may be justified in down voting these marketing answers.
However, I think that for reasons already mentioned (i.e. product is not open-source, is not available from official repositories) - that alternative responses may naturally be upvoted in relation to the product ads because they might be more elegant, easier to follow, etc...and perhaps very little needs to be done?...
My personal feeling is that at least a downvote is warranted with a comment describing the reason (marketing for closed-source software not available from official repositories, OR EVEN, improve this answer by creating an appropriate PPA, etc.).
