What about the source imagery data?

[Seyed-Ali-Ahmadi]

Is the corresponding imagery provided? Or can it be retrieved somehow?

Based on the introduction information, "The training set consists of 5 million labeled images. Majority of the satellite images cover diverse residential areas in the US. For the sake of good set representation, we have enriched the set with samples from various areas covering mountains, glaciers, forests, deserts, beaches, coasts, etc. Images in the set are of 256x256 pixel size with 1 ft/pixel resolution."

If there's no downloading option for the researchers, is there any other way to access the imagery to train machine learning models?

[nikolatr]

All I can say is that the training data is still not signed off for public release, unfortunately.