Donna, I would use those as I would the Frixion brand - with extreme caution. Although the thermo ink will dissipate, I suspect that, like the Frixion brand, there is a gel component that remains. Herra marker or painter's tape is all I am comfortable using on the front of any fabric that is not in a seam allowance.
Re Carol Doak's paper: Yes, it is the same as newsprint. I buy newsprint by the ream from Amazon. Always under $10, usually about $6. If I cannot get that when needed, I look at school writing paper (the kind of paper that primary children learn to write on). Even if it has blue lines on it, I can still use it. Both run through my printer with no issues.