Who's satellites does this use? I remember planet.com had a free tier too, then went entirely pay walled.
On a related note: I think it's kind of puzzling that all this data is freely available but seems to be rather complicated to access. One would assume building/operating satellites is more complex than making that data available in formats the average startup web developer can use almost instantly. IMHO you can see a similar pattern in weather data: it seems like there are a bunch of platforms which are basically wrapping public weather service's domain specific formats in a 'nicer' REST API. One could argue there's documentation on these formats, just read the docs, duh. However, I think lowering the barrier to entry by providing easy access and documentation could enable way more people to work with this data.
IMHO if you know some basic python and know your way around the requests library, it should be trivial for you to get started working with these datasets. That's just my personal opinion based on my experiences from a few years ago. Maybe it's way easier by now and there's a bunch of great free open APIs for this stuff. It always feels like they fulfill all the basic requirements to open the dataset and write some documentation but the last (small) step of writing the basic 'getting started' docs/blog posts and maybe some REST API for access is missing. Instead, confronted with lower than expected usage, a bunch of industry-transfer projects are spun-up to increase adoption. I guess DX also matters for open data hosted by public entities. /rant
[2] https://dataspace.copernicus.eu/
[3] https://browser.dataspace.copernicus.eu