what do you think...safe for basementor a gimmic?
It comes with the typical advisory based on the calcium chloride test that it should not be used if the concrete emits more than 3lbs of water vapour per 1000 sf over 24 hours.
More accurate than that test are instrumented tests, preferably taken midway into the slab.
Here is a link that might be useful: Guide to Flooring Moisture Problems
interesting link but how does a homeowner do these tests....where do I get the calcium etc etc...
Various acceptable methods are mentioned by the manufacturers cited in the link--everything from the old standby of applying 2'x2' sheets of polyethylene to the slab and waiting to see if moisture shows up, to electronic moisture meters. Unfortunately, the most accurate method according to the senior scientist of the Portland Cement Association is from sensors placed halfway into the slab. (See link to webinar on measuring humidity in concrete.)
But even using these tests on your basement floor are no guarantee though. Moisture in the slab is not a static thing. Moisture migrates through the slab through capillary action, hydrostatic pressure, leaks and water vapour. So while even the most accurate tests may show acceptable RH at the time of the test, rising water tables, storms etc. can raise RH.
The best protection is to provide a moisture insensitive material atop the slab that permits drying without affecting any moisture sensitive floor covering above it.
The referenced underlayment in your original post is cross-linked polyethylene, which will trap moisture and feed mould growth if the tests are inaccurate or conditions change.
Here is a link that might be useful: Moisture measurement in concrete