Thanks. I am glad you enjoy Planttext, and I hope you do use it in your company.
Regarding security though, as I state in some of the documentation, I would not recommend using PlantText to work on or store any sensitive diagrams. The reason is that any diagrams you work on are being sent to the PlantUML server in order to create the diagram images. I am not affiliated directly with that project and can not promise that it is in any way secure. In fact the requests to that server are not secured over SSL.
But, if you install your own PlantUML server at your company and use it from PlantText.com, then it can be secure. You can read how to install your own PlantUML server here . You just need to explain to any of your users that they need to change the PlantUML server URL in the Settings page of PlantText. Once you do that, the server used to convert the PlantUML code to diagram images is on your own network. At that point PlantText is only being used to save your documents and all that communication is secured over SSL.
On a related note, I am starting to get back to PlantText development, and I plan to release a new version, which does not allow any more documents to be saved to my server. Instead, it allows users to store any number of documents locally in browser storage. This makes it even more secure because the documents stay within your network completely, as long as you install your own PlantUML server of course.
I do not have any commercial or enterprise license right now, but you could be the first for the right price!!! 🙂
I hope this helps. And let me know what you end up doing and if I can help out any more. You can email me directly at firstname.lastname@example.org if you want to discuss any of this further. Perhaps a phone call even.