1. If it is received in the nature of salary (let's say payment on a monthly basis) the same will be taxed under the head salary and sec 44ADA will not come into the picture. Since sec 44ADA deals with presumptive taxation of an assessee engaged in profession specified u/s 44AA.
2. If the same was done as a profession (based on each task ) it will be considered as professional income and it will be covered u/s 44ADA.
3. Income cannot be taxed under sec 44ADA it is an option available to the assessee engaged in profession specified u/s 44AA to show his income and pay tax according to sec 44ADA.
4. One important criterion for determining the nature of income would be the deduction of TDS. If TDS is deducted u/s 192 while making the payment the same shall be taxed under the head salary and if TDS is deducted u/s 194J then it will be considered as professional income and the same shall be taxed as PGBP and sec 44ADA will be applicable in such a case.
Please correct me if the above solution has an alternative view.