fooot is correct on all counts, and this issue is generally covered by our user behavior policy, but I'll just add my take on the problems specific to this case since I was one of the people who deleted the original posts.
First, and this is a really big one, he/they are not disclosing their interest in the product. If the posts started with a disclaimer of "Full disclosure: this is a product I'm working on" then I think there would be less of an issue.
The big reason it's spamming, and not just "helpful information" is that it looks like it's coming from the community, when in reality it hasn't been vetted by any community members. If someone from the community (who has contributed in other ways) had used their product, and wanted to recommend it, that would have been fine.
Third, we have a general policy that all of your posts can't be self-promotion. It's an indication that you haven't joined to actually contribute; you only want to see what you can get out of the community. It's a culture we want to strongly discourage.
Lastly, even on a site with no paid ads, we do have a way for people to truly advertise products which have been vetted by the community: Community Ads. If this user was in good standing with the community, it could be suggested there, and the community could decide whether it's a product that they want advertised all over the site. Supporting small businesses that do good things for aviation isn't out of the realm of possibilities for community ads. Although, at this point I would guess this user(s) has destroyed any good will the community would have had towards them and their products.