PlantUML now can generate diagrams other than UML. In such cases the usual @startuml does not make sense anymore. So now we allow diagrams start with @startXYZ and finish with @endXYZ, where XYZ can change with the type of diagram and can be any characters (including spaces).
This means that plugin developers are encouraged to change their code to recognize @start instead of @startuml.
DITAA diagrams are usually formatted as @startditaa...@endditaa.
Ditaa is an Open Source project that allows to generate general diagrams from a text descriptions. The idea is close to PlantUML, and it may be useful for documentation to generate other diagrams than UML. So last version of PlantUML allows this :
You will find here the complete documentation about this. If your plugin does not support @startditaa yet, a temporary feature has been set up : it is also possible to use Ditaa with @startuml by using ditaa keyword on the very first line of your description. You can also use some option, after the @startditaa or @ditaa keyword: