The article is a good brief introduction to the concept of what we are now calling "Dyson sphere" (DS).
A few minor comments
1. Using SI units (in parantheses, for example) would be of very much help for (non- Anglo-Saxon) readers.
2. "It appears that alien civilizations, if they exist in our neighborhood, do not wish to communicate by radio." It is not clear if this sentence is a conclusion by Drake (as it seems to be, from the next para in the article) or belongs to the author. The sentence is obviously non-positive in nature and subjected to speculation. My feeling is that it is not necessary and should be removed UNLESS it is the conclusion of FD .
3. "...to get rid of waste heat, which must be radiated...". For puritans this may be controversial because radiation is not assimilated to heat by everybody (dS/dQ=1/T for heat while dS/dF=(4/3T); where S,Q,F refer to entropy, heat, radiation energy fluxes, respectively; T is an appropriately defined temperature)
4. "300 degrees Kelvin". The SI unit is simply Kelvin.
5. "This remark gave to readers the misleading impression that the habitat of an alien civilization would be a big round ball with a star at the center." That is true. However, it is not Dyson's fault for this interpretation of the DS as a continuous sphere. [Otherwise we have to claim that Cauchy put the fundamental of mathematics on the non-measurable notion of infinity when he first rigorously defined the concept of limit.]
6. "..and would never have been given the misleading name "Dyson spheres"". I would relax this LAST sentence, which might leave the overall impression that the article itself has no justification. The discussion in terms of Stapledon cloud and DS is interesting but should be moved inside the text.
(have sent comments to Dr. Dyson privately) This is a very good description of Dyson Spheres (DSs) and the status of searches for them to this time. The science on which DSs are based have been accurately described. My only suggestion would be to include a short section on how one can distinguish between DSs and stars surrounded by naturally occuring circumstellar dust cocoons. As it is, the reader is left to wonder how one can distinguish between them.