People probably mistook "by that time" as "at that time" instead of "since", which was what you meant. Also, use "has been" instead of "is", as the open-sourcin

People probably mistook "by that time" as "at that time" instead of "since", which was what you meant. Also, use "has been" instead of "is", as the open-sourcing happened sometime in the past (although it is in the state of open-source now).