This is pretty misleading: a lot of the presented open source equivalents are nothing like the original. For example, comparing HDFS to Colossus is... optimistic? Having used / worked on/with both, the similarity is roughly that they both store bytes. This would be a lot less misleading if there were annotations and if the "open source/real world" didn't mix together other large companies' products with open source. For example protobuf is open source, but this makes it look like it isn't.