Drylok is a masonry sealant which is inert when dried/cured. It does not promote mold growth, nor does it inhibit it- it's inert. There is a newer product under the Drylok name that contains mold inhibitors, but these types of chemicals are usually discouraged in animal enclosures.
I've seen original Drylok used in aquaria and vivaria by experienced keepers without apparent issue, and I used it to seal the inside of my plywood ball python enclosure. I use a soil-type substrate covered with leaf litter and large chunks of oak bark, and the soil is consistently moist enough to support ficus and philodendrons.
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